@article{wang_lin_dinh_2023, title={Data coverage assessment on neural network based digital twins for autonomous control system}, volume={182}, ISSN={["1873-2100"]}, DOI={10.1016/j.anucene.2022.109568}, abstractNote={In a recently developed Nearly Autonomous Management and Control (NAMAC) system, neural networks (NNs) are used to develop digital twins for diagnosis (DT-Ds). However, NNs are not usually considered extrapolation models and may result in large errors if they are applied to unseen data outside the training data (uncovered). In this study, we propose a data coverage assessment (DCA) to determine if the NN-based DT-Ds are extrapolated based on their epistemic uncertainty. The uncertainty quantification algorithms and uncertainty thresholds are selected based on the confusion matrix of classifying evaluation data into covered or uncovered data. To demonstrate the adaptability of the proposed framework, we applied it to a basic feedforward neural network and a more advanced recurrent neural network based on a more nonlinear database. Case studies show that the proposed framework can distinguish unseen data for both basic and advanced applications with proper uncertainty quantification algorithms and thresholds.}, journal={ANNALS OF NUCLEAR ENERGY}, author={Wang, Longcong and Lin, Linyu and Dinh, Nam}, year={2023}, month={Mar} }
 @article{iskhakov_leite_merzari_dinh_2023, title={Data-Driven High-to-Low for Coarse Grid System Thermal Hydraulics}, volume={4}, ISSN={["1943-748X"]}, url={https://doi.org/10.1080/00295639.2023.2180987}, DOI={10.1080/00295639.2023.2180987}, abstractNote={Traditional one-dimensional system thermal-hydraulic analysis has been widely applied in the nuclear industry for licensing purposes because of its numerical efficiency. However, such tools have inherently limited opportunities for modeling multiscale multidimensional flows in large reactor enclosures. Recent interest in three-dimensional coarse grid (CG) simulations has shown their potential in improving the predictive capability of system-level analysis. At the same time, CGs do not allow one to accurately resolve and capture turbulent mixing and stratification, whereas implemented in CG solvers relatively simple turbulence models exhibit large model form uncertainties. Therefore, there is a strong interest in further advances in CG modeling techniques. In this work, two high-to-low data-driven (DD) methodologies (and their combination) are explored to reduce grid and model-induced errors using a case study based on the Texas A&M upper plenum of a high-temperature gas-cooled reactor facility. The first approach relies on the use of a DD turbulence closure [eddy viscosity predicted by a neural network (NN)]. A novel training framework is suggested to consider the influence of grid cell size on closure. The second methodology uses a NN to predict velocity errors to improve low-fidelity results. Both methodologies and their combination have shown the potential to improve CG simulation results by using data with higher fidelity.}, journal={NUCLEAR SCIENCE AND ENGINEERING}, author={Iskhakov, Arsen S. and Leite, Victor Coppo and Merzari, Elia and Dinh, Nam T.}, year={2023}, month={Apr} }
 @article{iskhakov_tai_bolotnov_nguyen_merzari_shaver_dinh_2023, title={Data-Driven RANS Turbulence Closures for Forced Convection Flow in Reactor Downcomer Geometry}, volume={3}, ISSN={["1943-7471"]}, url={https://doi.org/10.1080/00295450.2023.2185056}, DOI={10.1080/00295450.2023.2185056}, abstractNote={Recent progress in data-driven turbulence modeling has shown its potential to enhance or replace traditional equation-based Reynolds-averaged Navier-Stokes (RANS) turbulence models. This work utilizes invariant neural network (NN) architectures to model Reynolds stresses and turbulent heat fluxes in forced convection flows (when the models can be decoupled). As the considered flow is statistically one dimensional, the invariant NN architecture for the Reynolds stress model reduces to the linear eddy viscosity model. To develop the data-driven models, direct numerical and RANS simulations in vertical planar channel geometry mimicking a part of the reactor downcomer are performed. Different conditions and fluids relevant to advanced reactors (sodium, lead, unitary-Prandtl number fluid, and molten salt) constitute the training database. The models enabled accurate predictions of velocity and temperature, and compared to the baseline k−τ turbulence model with the simple gradient diffusion hypothesis, do not require tuning of the turbulent Prandtl number. The data-driven framework is implemented in the open-source graphics processing unit–accelerated spectral element solver nekRS and has shown the potential for future developments and consideration of more complex mixed convection flows.}, journal={NUCLEAR TECHNOLOGY}, author={Iskhakov, Arsen S. and Tai, Cheng-Kai and Bolotnov, Igor A. and Nguyen, Tri and Merzari, Elia and Shaver, Dillon R. and Dinh, Nam T.}, year={2023}, month={Mar} }
 @article{tai_nguyen_iskhakov_merzari_dinh_bolotnov_2023, title={Direct Numerical Simulation of Low and Unitary Prandtl Number Fluids in Reactor Downcomer Geometry}, volume={6}, ISSN={["1943-7471"]}, DOI={10.1080/00295450.2023.2213286}, abstractNote={Mixed convection of low and unitary Prandtl fluids in a vertical passage is fundamental to passive heat removal in liquid metal and gas-cooled advanced reactor designs. Capturing the influence of buoyancy in flow and heat transfer in engineering analysis is hence a cornerstone to the safety of the next-generation reactor. However, accurate prediction of the mixed convection phenomenon has eluded current turbulence and heat transfer modeling approaches, yet further development and validation of modeling methods is limited by a scarcity of high-fidelity data pertaining to reactor heat transfer. In this work, a series of direct numerical simulations was conducted to investigate the influence of buoyancy on descending flow of liquid sodium, lead, and unitary Prandtl fluid in a differentially heated channel that represents the reactor downcomer region. From time-averaged statistics, flow-opposing/aiding buoyant plumes near the heated/cooled wall distort the mean velocity distribution, which gives rise to promotion/suppression of turbulence intensity and modification of turbulent shear stress and heat flux distribution. Frequency analysis of time series also suggests the existence of large-scale convective and thermal structures rising from the heated wall. As a general trend, fluids of lower Prandtl number were found to be more susceptible to the buoyancy effect due to stronger differential buoyancy across the channel. On the other hand, the effectiveness of convective heat transfer of the three studied fluids showed a distinct trend against the influence of buoyancy. Physical reasoning on observation of the Nusselt number trend is also discussed.}, journal={NUCLEAR TECHNOLOGY}, author={Tai, Cheng-Kai and Nguyen, Tri and Iskhakov, Arsen S. and Merzari, Elia and Dinh, Nam T. and Bolotnov, Igor A.}, year={2023}, month={Jun} }
 @article{iskhakova_kondo_tanimoto_dinh_bolotnov_2023, title={Interface Capturing Flow Boiling Simulations in a Compact Heat Exchanger}, volume={145}, ISSN={["2832-8469"]}, DOI={10.1115/1.4056688}, abstractNote={Abstract}, number={4}, journal={ASME JOURNAL OF HEAT AND MASS TRANSFER}, author={Iskhakova, Anna and Kondo, Yoshiyuki and Tanimoto, Koichi and Dinh, Nam T. and Bolotnov, Igor A.}, year={2023}, month={Apr} }
 @article{iskhakov_dinh_leite_merzari_2023, title={Machine learning from RANS and LES to inform coarse grid simulations}, volume={163}, ISSN={["1878-4224"]}, DOI={10.1016/j.pnucene.2023.104809}, abstractNote={Nuclear system thermal hydraulic analysis has historically relied on computationally inexpensive 1D codes. However, such tools are unable to capture multiscale multidimensional effects in large nuclear reactor enclosures. On the other hand, simulations with higher fidelity can be too expensive for such purposes. One of the ways to reduce computational cost is to perform simulations on a coarse grid, which, unfortunately, introduces large discretization errors. In this paper, two high-to-low data-driven approaches are investigated: (1) a coarse grid turbulence model to predict eddy viscosity and (2) correction of errors in coarse grid velocity fields. The approaches aim to reduce grid- and turbulence model-induced errors in coarse grid Reynolds-averaged Navier–Stokes (RANS) simulations. Two sources of high-fidelity data, RANS and large eddy simulations (LES), are explored. To extract the eddy viscosity from the LES data, an inverse optimization problem is solved. However, the LES eddy viscosity is shown to be comparable to the RANS eddy viscosity in terms of error reduction. Therefore, the directly available RANS eddy viscosity was used to develop a coarse grid data-driven turbulence model. Additionally, error correction in velocity is used to reduce the remaining uncertainties and bring the results closer to reality. The performance of the frameworks is demonstrated for a scaled upper plenum of a gas-cooled reactor facility.}, journal={PROGRESS IN NUCLEAR ENERGY}, author={Iskhakov, Arsen S. and Dinh, Nam T. and Leite, Victor Coppo and Merzari, Elia}, year={2023}, month={Sep} }
 @article{liu_dinh_sun_hu_2023, title={Uncertainty Quantification for Multiphase Computational Fluid Dynamics Closure Relations with a Physics-Informed Bayesian Approach}, volume={2}, ISSN={["1943-7471"]}, DOI={10.1080/00295450.2022.2162792}, abstractNote={Abstract Multiphase Computational Fluid Dynamics (MCFD) based on the two-fluid model is considered a promising tool to model complex two-phase flow systems. MCFD simulation can predict local flow features without resolving interfacial information. As a result, the MCFD solver relies on closure relations to describe the interaction between the two phases. Those empirical or semi-mechanistic closure relations constitute a major source of uncertainty for MCFD predictions. In this paper, we leverage a physics-informed uncertainty quantification (UQ) approach to inversely quantify the closure relations’ model form uncertainty in a physically consistent manner. This proposed approach considers the model form uncertainty terms as stochastic fields that are additive to the closure relation outputs. Combining dimensionality reduction and Gaussian processes, the posterior distribution of the stochastic fields can be effectively quantified within the Bayesian framework with the support of experimental measurements. As this UQ approach is fully integrated into the MCFD solving process, the physical constraints of the system can be naturally preserved in the UQ results. In a case study of adiabatic bubbly flow, we demonstrate that this UQ approach can quantify the model form uncertainty of the MCFD interfacial force closure relations, thus effectively improving the simulation results with relatively sparse data support.}, journal={NUCLEAR TECHNOLOGY}, author={Liu, Yang and Dinh, Nam and Sun, Xiaodong and Hu, Rui}, year={2023}, month={Feb} }
 @article{iskhakov_tai_bolotnov_dinh_2022, title={A Perspective on Data-Driven Coarse Grid Modeling for System Level Thermal Hydraulics}, volume={9}, ISSN={["1943-748X"]}, url={https://doi.org/10.1080/00295639.2022.2107864}, DOI={10.1080/00295639.2022.2107864}, abstractNote={Abstract In the future, advanced reactors are expected to play an important role in nuclear power. However, their development and deployment are hindered by the absence of reliable and efficient models for analysis of system thermal hydraulics (TH). For instance, mixing and thermal stratification in reactor enclosures cannot be captured by traditional one-dimensional system codes, yet usage of high-resolution solvers is computationally expensive. Recent developments of coarse grid (CG) and system codes with three-dimensional capabilities have shown that they are promising tools for system-level analysis. However, these codes feature large turbulence model form and discretization errors and require further improvements to capture turbulent effects during complex transients. Improvements can be achieved by using data-driven (DD) approaches. This paper provides an overview of recent applications of DD methods in the areas of fluid dynamics and TH. It is demonstrated that they are being widely applied for engineering-scale analysis (e.g., closures for large eddy simulations/Reynolds-averaged Navier-Stokes using direct numerical simulation data). However, they cannot be directly employed for the system scale because of some features of the latter: usage of CG, transient nature of the considered phenomena, nonlinear interaction of multiple closures, etc. At the same time, accumulated experience allows outlining of potential frameworks for further developments in DD CG modeling of system-level TH.}, journal={NUCLEAR SCIENCE AND ENGINEERING}, publisher={Informa UK Limited}, author={Iskhakov, Arsen S. and Tai, Cheng-Kai and Bolotnov, Igor A. and Dinh, Nam T.}, year={2022}, month={Sep} }
 @article{zhu_dinh_saini_bolotnov_2022, title={An adaptive knowledge-based data-driven approach for turbulence modeling using ensemble learning technique under complex flow configuration: 3D PWR sub-channel with DNS data}, volume={393}, ISSN={["1872-759X"]}, DOI={10.1016/j.nucengdes.2022.111814}, abstractNote={This work describes a new approach to increase the accuracy of Reynolds-averaged Navier–Stokes (RANS) in modeling turbulence flow leveraging the machine learning technique. Traditionally, different turbulence models for Reynolds stress are developed for different flow patterns based on human knowledge. Each turbulence model has a certain application domain and prediction uncertainty. In recent years, with the rapid improvements of machine learning techniques, researchers start to develop an approach to compensate for the prediction discrepancy of traditional turbulence models with statistical models and data. However, the approach has deficiencies in several aspects. For example, the amount of human knowledge introduced to the statistical model couldn’t be controlled, which makes the statistical model learn from a very naïve stage and limits its application. In this work, a new approach is developed to address those deficiencies. The new approach uses the “ensemble learning” technique to control the amount of human knowledge introduced into the statistical model. Therefore, the new approach could be adaptive to the multiple application domains. According to the results of case study, the new approach shows higher accuracy than both traditional turbulence models and the previous machine learning approach.}, journal={NUCLEAR ENGINEERING AND DESIGN}, author={Zhu, Yangmo and Dinh, Nam T. and Saini, Nadish and Bolotnov, Igor A.}, year={2022}, month={Jul} }
 @article{gurgen_dinh_2022, title={Development and assessment of a reactor system prognosis model with physics-guided machine learning}, volume={398}, ISSN={["1872-759X"]}, DOI={10.1016/j.nucengdes.2022.111976}, abstractNote={Autonomous control systems provide recommendations to help operators in decision-making during plant operations ranging from normal operation to accident management. An important step of autonomous control is prognosis. In nuclear engineering domain, prognosis is the process of predicting future conditions of a system or equipment based on present signs and symptoms of a fault. The prognosis model allows predicting future reactor states for possible candidate control strategies so that the outcomes can be evaluated to determine the best control strategy. The prognosis model requires representing direct relationships between the symptoms and the predictions. In nuclear engineering, computational simulations are approximate representations of the operation of the real system. However, prognosis with computational simulations requires high computation power and time due to possible large number of scenarios. Necessary computation resources can be reduced with machine learning (ML) approach for fast predictions by building a surrogate function using the simulation data. A critical issue is, ML models are ignorant of physical knowledge, and these models approximate statistical relationships between the system variables. This ignorance can produce results that are inconsistent with physical laws, even if an optimal result is achieved from a mathematical point of view. Physics-guided machine learning (PGML) is an approach to tackle this issue. This work formulates and illustrates a framework to guide development and assessment of the ML-based prognosis model for autonomous control systems. The development of the prognosis model considers the training of a ML model which consists of optimizing many aspects of the ML approach. The assessment of the prognosis model considers training data limitations and uncertainties of the ML approach. Prognosis models with standalone ML and PGML are developed and assessed on the loss-of-flow scenario of Experimental Breeder Reactor II. The results indicate that PGML based prognosis model has the best performance compared to other prognosis models.}, journal={NUCLEAR ENGINEERING AND DESIGN}, author={Gurgen, Anil and Dinh, Nam T.}, year={2022}, month={Nov} }
 @article{lin_gurgen_dinh_2022, title={Development and assessment of prognosis digital twin in a NAMAC system}, volume={179}, ISSN={["1873-2100"]}, DOI={10.1016/j.anucene.2022.109439}, abstractNote={The nearly autonomous management and control (NAMAC) system is a comprehensive control system to assist plant operations by furnishing control recommendations to operators. Prognosis digital twin (DT-P) is a critical component in NAMAC for predicting action effects and supporting NAMAC decision-making during normal and accident scenarios. To quantifying and reducing uncertainty of machine-learning-based DT-Ps in multi-step predictions, this work investigates and derives insights from the application of three techniques for optimizing the performance of DT-P by long short-term memory recurrent neural networks, including manual search, sequential model-based optimization, and physics-guided machine learning. Sequential model-based optimization and physics-guide machine learning result in smallest errors when the predicting transients are similar to the training data.}, journal={ANNALS OF NUCLEAR ENERGY}, author={Lin, Linyu and Gurgen, Anil and Dinh, Nam}, year={2022}, month={Dec} }
 @article{lin_athe_rouxelin_avramova_gupta_youngblood_lane_dinh_2022, title={Digital-twin-based improvements to diagnosis, prognosis, strategy assessment, and discrepancy checking in a nearly autonomous management and control system}, volume={166}, ISSN={["1873-2100"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85115958204&partnerID=MN8TOARS}, DOI={10.1016/j.anucene.2021.108715}, abstractNote={The Nearly Autonomous Management and Control System (NAMAC) is a comprehensive control system that assists plant operations by furnishing control recommendations to operators in a broad class of situations. This study refines a NAMAC system for making reasonable recommendations during complex loss-of-flow scenarios with a validated Experimental Breeder Reactor II simulator, digital twins improved by machine-learning algorithms, a multi-attribute decision-making scheme, and a discrepancy checker for identifying unexpected recommendation effects. We assess the performance of each NAMAC component, while we demonstrate and evaluated the capability of NAMAC in a class of loss-of-flow scenarios.}, journal={ANNALS OF NUCLEAR ENERGY}, author={Lin, Linyu and Athe, Paridhi and Rouxelin, Pascal and Avramova, Maria and Gupta, Abhinav and Youngblood, Robert and Lane, Jeffrey and Dinh, Nam}, year={2022}, month={Feb} }
 @article{hanna_son_dinh_2021, title={AI-Guided Reasoning-Based Operator Support System for the Nuclear Power Plant Management}, volume={154}, ISSN={["1873-2100"]}, DOI={10.1016/j.anucene.2020.108079}, abstractNote={The decision-making process in the Nuclear Power Plant (NPP) control room faces some challenges: operator incomplete knowledge, insufficient time for responding to the highly dynamic events, and a large number of indicators to monitor. Because of the complexity of the NPP system, it is hard to pre-plan all the failures/mitigative actions. An intelligent operator support system is vital to mitigate these shortcomings. In this paper, an AI declarative approach (Answer Set Programming (ASP)) is employed to represent our knowledge of the nuclear power plant in the form of logic rules. This represented knowledge is structured to form a reasoning-based operator support system. When an incident occurs, this ASP-based reasoning support system is demonstrated to be capable of fault identification (diagnosis), informing the operator of different scenarios and consequences, and generating the control options (decision making).}, journal={ANNALS OF NUCLEAR ENERGY}, author={Hanna, Botros and Son, Tran Cao and Dinh, Nam}, year={2021}, month={May} }
 @article{bao_feng_dinh_zhang_2021, title={Deep learning interfacial momentum closures in coarse-mesh CFD two-phase flow simulation using validation data}, volume={135}, ISSN={["1879-3533"]}, DOI={10.1016/j.ijmultiphaseflow.2020.103489}, abstractNote={Multiphase flow phenomena have been widely observed in the industrial applications, yet it remains a challenging unsolved problem. Three-dimensional computational fluid dynamics (CFD) approaches resolve of the flow fields on finer spatial and temporal scales, which can complement dedicated experimental study. However, closures must be introduced to reflect the underlying physics in multiphase flow. Among them, the interfacial forces, including drag, lift, turbulent-dispersion and wall-lubrication forces, play an important role in bubble distribution and migration in liquid-vapor two-phase flows. Development of those closures traditionally rely on the experimental data and analytical derivation with simplified assumptions that usually cannot deliver a universal solution across a wide range of flow conditions. In this paper, a data-driven approach, named as feature-similarity measurement (FSM), is developed and applied to improve the simulation capability of two-phase flow with coarse-mesh CFD approach. Interfacial momentum transfer in adiabatic bubbly flow serves as the focus of the present study. Both a mature and a simplified set of interfacial closures are taken as the low-fidelity data. Validation data (including relevant experimental data and validated fine-mesh CFD simulations results) are adopted as high-fidelity data. Qualitative and quantitative analysis are performed in this paper. These reveal that FSM can substantially improve the prediction of the coarse-mesh CFD model, regardless of the choice of interfacial closures. It demonstrates that data-driven methods can aid the multiphase flow modeling by exploring the connections between local physical features and simulation errors.}, journal={INTERNATIONAL JOURNAL OF MULTIPHASE FLOW}, author={Bao, Han and Feng, Jinyong and Dinh, Nam and Zhang, Hongbin}, year={2021}, month={Feb} }
 @article{lin_athe_rouxelin_avramova_gupta_youngblood_lane_dinh_2021, title={Development and assessment of a nearly autonomous management and control system for advanced reactors}, volume={150}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85091738050&partnerID=MN8TOARS}, DOI={10.1016/j.anucene.2020.107861}, abstractNote={This paper develops a Nearly Autonomous Management and Control (NAMAC) system for advanced reactors. The development process of NAMAC is characterized by a three layer-layer architecture: knowledge base, the Digital Twin (DT) developmental layer, and the NAMAC operational layer. The DT is described as a knowledge acquisition system from the knowledge base for intended uses in the NAMAC system. A set of DTs with different functions is developed with acceptable performance and assembled according to the NAMAC operational workflow to furnish recommendations to operators. To demonstrate the capability of the NAMAC system, a case study is designed, where a baseline NAMAC is implemented for operating a simulator of the Experimental Breeder Reactor II during a single loss of flow accident. When NAMAC is operated in the training domain, it can provide reasonable recommendations that prevent the peak fuel centerline temperature from exceeding a safety criterion.}, journal={Annals of Nuclear Energy}, author={Lin, L. and Athe, P. and Rouxelin, P. and Avramova, M. and Gupta, A. and Youngblood, R. and Lane, J. and Dinh, N.}, year={2021} }
 @book{dinh_2021, title={Development of a Nearly Autonomous Management and Control (NAMAC) System for Advanced Reactors (Final Report for ARPA-E Project)}, url={https://doi.org/10.2172/1866087}, DOI={10.2172/1866087}, author={Dinh, Nam}, year={2021}, month={Dec} }
 @article{lee_lin_athe_dinh_2021, title={Development of the Machine Learning-based Safety Significant Factor Inference Model for Diagnosis in Autonomous Control System}, volume={162}, ISSN={["1873-2100"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85109449538&partnerID=MN8TOARS}, DOI={10.1016/j.anucene.2021.108443}, abstractNote={As a critical component to the autonomous control system, Digital Twin for Diagnosis (DT-D) is a virtual replica of physical systems for an accurate understanding of reactor states. Since the physical damage state cannot be measured directly in transient or accident conditions, safety significant factor (SSF) is introduced as a surrogate index for physical damage states to support safety-related decision making. This study develops a machine learning (ML) based SSF inference model (SSFIM) using the Recurrent Neural Network (RNN) with acceptable accuracy, generalization capability, effectiveness, and robustness against sensor errors. To demonstrate the capability of the ML-based SSFIM, case studies are implemented on a plant simulator for Experimental Breeder Reactor – II. For partial loss of flow accident scenarios, the SSFIM is able to infer the peak fuel centerline temperature with minimally one sensor. Meanwhile the SSFIM is also found to be robust against manipulated sensor drifts and/or random noises.}, journal={ANNALS OF NUCLEAR ENERGY}, author={Lee, Joomyung and Lin, Linyu and Athe, Paridhi and Dinh, Nam}, year={2021}, month={Nov} }
 @book{lin_lee_poudel_mcjunkin_dinh_agarwal_2021, title={Enhancing the Operational Resilience of Advanced Reactors with Digital Twins by Recurrent Neural Networks}, url={https://doi.org/10.2172/1835892}, DOI={10.2172/1835892}, abstractNote={Because of a lack of operational data and uncertainty in evaluation model for abnormal and accident scenarios, the established operating procedures can be biased in characterizing the reactor states and ensuring operational resilience. To reduce uncertainty associated with actual plant conditions, digital twin (DT) technology is suggested to support operator’s decision-making by effectively extracting and using knowledge of the current and future plant states from the knowledge base. This study first builds a knowledge base based on the characterization of issue space and the simulation tool. Next, this study discusses diagnosis and prognosis DTs for enhancing operational resilience by recovering the complete states of reactors and by predicting the future reactor behaviors. Finally, the decision-making module of the control system can determine the optimal control strategy that meets operational goals during loss-of-flow scenarios. To demonstrate and evaluate the DTs capability for supporting the operations of nuclear reactors, this study develops and assesses both the diagnosis and prognosis DTs in a nearly autonomous management and control system for an Experimental Breeder Reactor-II simulator during different loss-of-flow scenarios.}, author={Lin, Linyu and Lee, Joomyung and Poudel, Bikash and McJunkin, Timothy and Dinh, Nam and Agarwal, Vivek}, year={2021}, month={Oct} }
 @article{lin_lee_poudel_mcjunkin_dinh_agarwal_2021, title={Enhancing the Operational Resilience of Advanced Reactors with Digital Twins by Recurrent Neural Networks}, DOI={10.1109/RWS52686.2021.9611796}, abstractNote={Because of a lack of operation data during abnormal and accident scenarios, along with the existence of uncertainty in the evaluation model for transient and accident analysis, the established abnormal and emergency operating procedures can be biased in characterizing the reactor states and ensuring operational resilience. To improve state awareness and ensure operational flexibility for minimizing effects on the system due to anomaly, digital twin (DT) technology is suggested to support operator's decision-making by effectively extracting and using knowledge of the current and future plant states from the knowledge base. To demonstrate DT's capability for recovering the complete states of reactors and for predicting the future reactor behaviors, this paper develops and assesses both the diagnosis and prognosis DTs in a nearly autonomous management and control system for an Experimental Breeder Reactor-II simulator during different loss-of-flow scenarios.}, journal={2021 RESILIENCE WEEK (RWS)}, author={Lin, Linyu and Lee, Joomyung and Poudel, Bikash and McJunkin, Timothy and Dinh, Nam and Agarwal, Vivek}, year={2021} }
 @article{iskhakov_dinh_chen_2021, title={Integration of neural networks with numerical solution of PDEs for closure models development}, volume={406}, ISSN={["1873-2429"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85107023012&partnerID=MN8TOARS}, DOI={10.1016/j.physleta.2021.127456}, abstractNote={The work is a continuation of a paper by Iskhakov A.S. and Dinh N.T. "Physics-integrated machine learning: embedding a neural network in the Navier-Stokes equations". Part I // arXiv:2008.10509 (2020) [1]. The proposed in [1] physics-integrated (or PDE-integrated (partial differential equation)) machine learning (ML) framework is furtherly investigated. The Navier-Stokes equations are solved using the Tensorflow ML library for Python programming language via the Chorin's projection method. The Tensorflow solution is integrated with a deep feedforward neural network (DFNN). Such integration allows one to train a DFNN embedded in the Navier-Stokes equations without having the target (labeled training) data for the direct outputs from the DFNN; instead, the DFNN is trained on the field variables (quantities of interest), which are solutions for the Navier-Stokes equations (velocity and pressure fields). To demonstrate performance of the framework, two additional case studies are formulated: 2D turbulent lid-driven cavities with predicted by a DFNN (a) turbulent viscosity and (b) derivatives of the Reynolds stresses. Despite its complexity and computational cost, the proposed physics-integrated ML shows a potential to develop a "PDE-integrated" closure relations for turbulent models and offers principal advantages, namely: (i) the target outputs (labeled training data) for a DFNN might be unknown and can be recovered using the knowledge base (PDEs); (ii) it is not necessary to extract and preprocess information (training targets) from big data, instead it can be extracted by PDEs; (iii) there is no need to employ a physics- or scale-separation assumptions to build a closure model for PDEs. The advantage (i) is demonstrated in the Part I paper [1], while the advantage (ii) is the subject of the current paper.}, journal={PHYSICS LETTERS A}, author={Iskhakov, Arsen S. and Dinh, Nam T. and Chen, Edward}, year={2021}, month={Aug} }
 @misc{lin_bao_dinh_2021, title={Uncertainty quantification and software risk analysis for digital twins in the nearly autonomous management and control systems: A review}, volume={160}, ISSN={["1873-2100"]}, DOI={10.1016/j.anucene.2021.108362}, abstractNote={A nearly autonomous management and control (NAMAC) system is designed to furnish recommendations to operators for achieving particular goals based on NAMAC’s knowledge base. As a critical component in a NAMAC system, digital twins (DTs) are used to extract information from the knowledge base to support decision-making in reactor control and management during all modes of plant operations. With the advancement of artificial intelligence and data-driven methods, machine learning algorithms are used to build DTs of various functions in the NAMAC system. To evaluate the uncertainty of DTs and its impacts on the reactor digital instrumentation and control systems, uncertainty quantification (UQ) and software risk analysis is needed. As a comprehensive overview of prior research and a starting point for new investigations, this study selects and reviews relevant UQ techniques and software hazard and software risk analysis methods that may be suitable for DTs in the NAMAC system.}, journal={ANNALS OF NUCLEAR ENERGY}, author={Lin, Linyu and Bao, Han and Dinh, Nam}, year={2021}, month={Sep} }
 @article{liu_wang_sun_liu_dinh_hu_2021, title={Uncertainty quantification for Multiphase-CFD simulations of bubbly flows: a machine learning-based Bayesian approach supported by high-resolution experiments}, volume={212}, ISSN={["1879-0836"]}, DOI={10.1016/j.ress.2021.107636}, abstractNote={In this paper, we developed a machine learning-based Bayesian approach to inversely quantify and reduce the uncertainties of multiphase computational fluid dynamics (MCFD) simulations for bubbly flows. The proposed approach is supported by high-resolution two-phase flow measurements, including those by double-sensor conductivity probes, high-speed imaging, and particle image velocimetry. Local distributions of key physical quantities of interest (QoIs), including the void fraction and phasic velocities, are obtained to support the Bayesian inference. In the process, the epistemic uncertainties of the closure relations are inversely quantified while the aleatory uncertainties from stochastic fluctuations of the system are evaluated based on experimental uncertainty analysis. The combined uncertainties are then propagated through the MCFD solver to obtain uncertainties of the QoIs, based on which probability-boxes are constructed for validation. The proposed approach relies on three machine learning methods: feedforward neural networks and principal component analysis for surrogate modeling, and Gaussian processes for model form uncertainty modeling. The whole process is implemented within the framework of an open-source deep learning library PyTorch with graphics processing unit (GPU) acceleration, thus ensuring the efficiency of the computation. The results demonstrate that with the support of high-resolution data, the uncertainties of MCFD simulations can be significantly reduced. The proposed approach has the potential for other applications that involve numerical models with empirical parameters.}, journal={RELIABILITY ENGINEERING & SYSTEM SAFETY}, author={Liu, Yang and Wang, Dewei and Sun, Xiaodong and Liu, Yang and Dinh, Nam and Hu, Rui}, year={2021}, month={Aug} }
 @article{lin_montanari_prescott_sampath_bao_dinh_2020, title={Adequacy evaluation of smoothed particle hydrodynamics methods for simulating the external-flooding scenario}, volume={365}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85086443497&partnerID=MN8TOARS}, DOI={10.1016/j.nucengdes.2020.110720}, abstractNote={Abstract In modern nuclear risk analysis for external-flooding scenarios, Computational Fluid Dynamics (CFD) tools are used to simulate the generation, propagation, and interactions of Nuclear Power Plants (NPPs) with the nuclear Systems, Structures, and Components (SSCs). Smoothed Particle Hydrodynamics (SPH), as a Lagrangian and mesh-free method, is one of the particle-based CFD methods. Since SPH methods can effectively handling large-scale fluid simulations with complex interfacial structures, SPH-based software has been used to simulate the impacts of external flood onto nuclear facilities, and the simulation results have been used to support nuclear safety analysis. However, previous risk analysis assumes that SPH methods and the corresponding simulation packages are applicable to the external-hazards risk analysis, and their simulation uncertainties do not affect the confidence of safety decision. Considering the high consequences to nuclear safety induced by simulation errors, a systematic and complete validation process is needed to evaluate the adequacy of SPH simulations in informing related safety decisions. In this study, a scoping-stage assessment is performed for SPH’s adequacy in simulating the real-scale external flooding scenarios, especially in predicting the surface-wave impacts on SSCs at NPP sites. To ensure the completeness and consistency, validation frameworks, Code Scalability Applicability and Uncertainty (CSAU), and its regulatory guide, Evaluation Model Development and Assessment Process (EMDAP) are followed to guide validation activities and to make final code adequacy assessment. First, an external-flooding scenario is designed, and SPH simulations are performed with an SPH-based software named Neutrino. A Phenomenon Identification and Ranking Table (PIRT) is created, and the surface-wave impacts are identified as one of the high-rank phenomena. At the same time, a performance measurement standard is created for measuring the code adequacy in informing safety decisions consistently and transparently. Next, numerical benchmarks are designed for assessing the code adequacy of SPH methods and corresponding software implementations on Neutrino. Next, code accuracy is evaluated by comparing simulation results from Neutrino against experimental measurements in each benchmark. Meanwhile, a scaling analysis is performed to determine a group of dimensionless number for characterizing important physics and to assess the applicability of validation database collected in reduced-scale facility to the prototypic scenario. Finally, results from all activities are brought together to make an adequacy decision. It is found that, based on the current evidence, SPH methods and associated Neutrino software can predict the unbroken surface-wave peak pressure onto stationary rigid with reasonable accuracy if the suggested sizes of particles are used. However, it is suggested by independent reviews that the validity of major assumptions in target applications need to be evaluated with large-scale experiments, and the relevancy of other phenomena like turbulence and air pockets need to be identified with more benchmarks. As for the SPH’s adequacy in predicting the impact forces on dynamic rigid, the available evidence is not sufficient to support the decisions.}, journal={Nuclear Engineering and Design}, author={Lin, L. and Montanari, N. and Prescott, S. and Sampath, R. and Bao, H. and Dinh, N.}, year={2020} }
 @article{hanna_trieu_son_dinh_2020, title={An Application of ASP in Nuclear Engineering: Explaining the Three Mile Island Nuclear Accident Scenario}, volume={20}, ISSN={["1475-3081"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85091989952&partnerID=MN8TOARS}, DOI={10.1017/S1471068420000241}, abstractNote={Abstract}, number={6}, journal={THEORY AND PRACTICE OF LOGIC PROGRAMMING}, author={HANNA, B. O. T. R. O. S. N. and TRIEU, L. Y. L. Y. T. and SON, T. R. A. N. C. and DINH, N. A. M. T.}, year={2020}, month={Nov}, pages={926–941} }
 @article{bao_feng_dinh_zhang_2020, title={Computationally efficient CFD prediction of bubbly flow using physics-guided deep learning}, volume={131}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85087640312&partnerID=MN8TOARS}, DOI={10.1016/j.ijmultiphaseflow.2020.103378}, abstractNote={To realize efficient computational fluid dynamics (CFD) prediction of two-phase flow, a multi-scale framework was proposed in this paper by applying a physics-guided data-driven approach. Instrumental to this framework, Feature Similarity Measurement (FSM) technique was developed for error estimation in two-phase flow simulation using coarse-mesh CFD, to achieve a comparable accuracy as fine-mesh simulations with fast-running feature. By defining physics-guided parameters and variable gradients as physical features, FSM has the capability to capture the underlying local patterns in the coarse-mesh CFD simulation. Massive low-fidelity data and respective high-fidelity data are used to explore the underlying information relevant to the main simulation errors and the effects of phenomenological scaling. By learning from previous simulation data, a surrogate model using deep feedforward neural network (DFNN) can be developed and trained to estimate the simulation error of coarse-mesh CFD. In a demonstration case of two-phase bubbly flow, the DFNN model well captured and corrected the unphysical “peaks” in the velocity and void fraction profiles near the wall in the coarse-mesh configuration, even for extrapolative predictions. The research documented supports the feasibility of the physics-guided deep learning methods for coarse mesh CFD simulations which has a potential for the efficient industrial design.}, journal={International Journal of Multiphase Flow}, author={Bao, H. and Feng, J. and Dinh, N. and Zhang, H.}, year={2020} }
 @article{bodda_gupta_dinh_2020, title={Enhancement of risk informed validation framework for external hazard scenario}, volume={204}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85088821078&partnerID=MN8TOARS}, DOI={10.1016/j.ress.2020.107140}, abstractNote={In recent years, the U.S. Nuclear Regulatory Commission (USNRC) and the International Atomic Energy Agency (IAEA) have developed methodologies to assess the vulnerabilities of nuclear plants against site specific extreme hazards. In many cases, advanced simulation tools are being considered to simulate multi-physics, multi-scale phenomena and to evaluate vulnerability of nuclear facilities. The credibility of advanced simulation tools is assessed based on a formal verification, validation, and uncertainty quantification procedure. One of the key limitations in validation is the lack of relevant experimental data at system-level. This limitation leads to a decrease in the confidence of system-level risk predictions. Therefore, a robust validation framework is needed to formalize the confidence in predictive capability of advanced simulation results. This study enhances the existing risk informed validation methodology, originally proposed by Kwag et al. [1] and Bodda et al. [2], by developing additional attributes and a new set of validation indicies for a complete and wider applicability of the framework. In this manuscript, the methodology to identify the critical path that leads to the system-level failure is illustrated. The overall validation is checked for completeness and consistency by comparing the critical path for both the system-level simulation and experimental models. The applicability of the code for an intended application is represented in terms of various maturity levels and helps in the process of decision making.}, journal={Reliability Engineering and System Safety}, author={Bodda, S.S. and Gupta, A. and Dinh, N.}, year={2020} }
 @article{hanna_dinh_youngblood_bolotnov_2020, title={Machine-learning based error prediction approach for coarse-grid Computational Fluid Dynamics (CG-CFD)}, volume={118}, ISSN={["1878-4224"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85072240790&partnerID=MN8TOARS}, DOI={10.1016/j.pnucene.2019.103140}, abstractNote={Computational Fluid Dynamics (CFD) is one of the modeling approaches essential to identifying the parameters that affect Containment Thermal Hydraulics (CTH) phenomena. While the CFD approach can capture the multidimensional behavior of CTH phenomena, its computational cost is high when modeling complex accident scenarios. To mitigate this expense, we propose reliance on coarse-grid CFD (CG-CFD). Coarsening the computational grid increases the grid-induced error thus requiring a novel approach that will produce a surrogate model predicting the distribution of the CG-CFD local error and correcting the fluid-flow variables. Given sufficiently fine-mesh simulations, a surrogate model can be trained to predict the CG-CFD local errors as a function of the coarse-grid local flow features. The surrogate model is constructed using Machine Learning (ML) regression algorithms. Two of the widely used ML regression algorithms were tested: Artificial Neural Network (ANN) and Random Forest (RF). The proposed CG-CFD method is illustrated with a three-dimensional turbulent flow inside a lid-driven cavity. We studied a set of scenarios to investigate the capability of the surrogate model to interpolate and extrapolate outside the training data range. The proposed method has proven capable of correcting the coarse-grid results and obtaining reasonable predictions for new cases (of different Reynolds number, different grid sizes, or larger geometries). Based on the investigated cases, we found this novel method maximizes the benefit of the available data and shows potential for a good predictive capability.}, journal={PROGRESS IN NUCLEAR ENERGY}, author={Hanna, Botros N. and Dinh, Nam T. and Youngblood, Robert W. and Bolotnov, Igor A.}, year={2020}, month={Jan} }
 @inproceedings{bao_feng_zhang_dinh_2020, title={Probing interfacial momentum closures in two-phase bubbly flow with machine learning-aided methods}, volume={122}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85092165854&partnerID=MN8TOARS}, DOI={10.13182/T122-32371}, booktitle={Transactions of the American Nuclear Society}, author={Bao, H. and Feng, J. and Zhang, H. and Dinh, N.}, year={2020}, pages={844–847} }
 @article{chang_fang_dinh_2020, title={Reynolds-Averaged Turbulence Modeling Using Deep Learning with Local Flow Features: An Empirical Approach}, volume={194}, ISSN={["1943-748X"]}, url={https://doi.org/10.1080/00295639.2020.1712928}, DOI={10.1080/00295639.2020.1712928}, abstractNote={Abstract Reynolds-Averaged Navier-Stoke (RANS) models offer an alternative avenue in predicting flow characteristics when the corresponding experiments are difficult to achieve due to geometry complexity, limited budget, or knowledge. RANS models require the knowledge of subgrid scale physics to solve conservation equations for mass, energy, and momentum. Mechanistic turbulence models, such as k-ε, are generally evaluated and calibrated for specific flow conditions with various degrees of uncertainty. These models have limited capability to assimilate a substantial amount of data due to model form constraints. Meanwhile, deep learning (DL) has been proven to be universal approximators with the potential to assimilate available, relevant, and adequately evaluated data. Moreover, deep neural networks (DNNs) can create surrogate models without knowing function forms. Such a data-driven approach can be used in updating fluid models based on observations as opposed to hard-wiring models with precalibrated correlations. The paper presents progress in applying DNNs to model Reynolds stress using two machine learning (ML) frameworks. A novel flow feature coverage mapping is proposed to quantify the physics coverage of DL-based closures. It can be used to examine the sufficiency of training data and input flow features for data-driven turbulence models. The case of a backward-facing step is formulated to demonstrate that not only can DNNs discover underlying correlation behind fluid data but also they can be implemented in RANS to predict flow characteristics without numerical stability issues. The presented research is a crucial stepping-stone toward the data-driven turbulence modeling, which potentially benefits the design of data-driven experiments that can be used to validate fluid models with ML-based fluid closures.}, number={8-9}, journal={NUCLEAR SCIENCE AND ENGINEERING}, publisher={Informa UK Limited}, author={Chang, Chih-Wei and Fang, Jun and Dinh, Nam T.}, year={2020}, month={Sep}, pages={650–664} }
 @article{bodda_gupta_dinh_2020, title={Risk informed validation framework for external flooding scenario}, volume={356}, ISSN={["1872-759X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85074190032&partnerID=MN8TOARS}, DOI={10.1016/j.nucengdes.2019.110377}, abstractNote={Safety of nuclear plants against external flooding has gained significant attention following the accident at Fukushima Daiichi nuclear power station. In United States, Oyster Creek nuclear plant was safely shutdown when high storm surge during hurricane Sandy caused a potential flooding threat. Subsequently, the nuclear energy industry experienced a significant activity in Probabilistic Risk Assessment (PRA) for external flooding. Increasingly, methods of computational fluid dynamics including advanced simulation codes are being considered to evaluate the sequence of events during different scenarios of flooding at a plant. One of the key limitations in the use of advanced codes for external flooding is related to a lack of credibility of such simulations. The motivation of this study is to develop a formal validation approach that provides a basis to quantify credibility of risk assessments that are based on advanced simulation codes. In this study, we illustrate the application of existing performance based risk-informed validation framework to an external flooding event. However, it is determined that a direct application of this approach to flooding is restricted due to a lack of relevant data to evaluate experimental fragilities for flooding failures. Therefore, we take a simple synthetic example to evaluate the applicability of the proposed framework to validation of flooding PRA scenario and update the proposed framework as needed.}, journal={NUCLEAR ENGINEERING AND DESIGN}, author={Bodda, Saran Srikanth and Gupta, Abhinav and Dinh, Nam}, year={2020}, month={Jan} }
 @article{bao_dinh_lin_youngblood_lane_zhang_2020, title={Using deep learning to explore local physical similarity for global-scale bridging in thermal-hydraulic simulation}, volume={147}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85087742174&partnerID=MN8TOARS}, DOI={10.1016/j.anucene.2020.107684}, abstractNote={Current system thermal–hydraulic codes have limited credibility in simulating real plant conditions, especially when the geometry and boundary conditions are extrapolated beyond the range of test facilities. Because mesh size is one of the model parameters for these coarse-mesh codes with simplified boundary-layer treatments, the mesh-induced error and model error are tightly connected, which makes it difficult to evaluate mesh effect or model scalability independently, as in classical scaling analysis. This paper proposes a data-driven approach, Feature-Similarity Measurement (FSM), to establish a technical basis to overcome these difficulties by exploring local patterns using machine learning. The underlying local patterns in multiscale data are represented by a set of physical features that embody the information from a physical system of interest, empirical correlations, and the effect of mesh size. After performing a limited number of high-fidelity numerical simulations and a sufficient amount of fast-running coarse-mesh simulations, an error database is built, and deep learning is applied to construct and explore the relationship between the local physical features and simulation errors. As a result, a data-driven model can be developed to provide an accurate estimate on the simulation error even when global-scale gaps exist. Case studies based on mixed convection have been designed for demonstrating the capability of data-driven models in bridging global-scale gaps.}, journal={Annals of Nuclear Energy}, author={Bao, H. and Dinh, N. and Lin, L. and Youngblood, R. and Lane, J. and Zhang, H.}, year={2020} }
 @inproceedings{bao_youngblood_zhang_dinh_lin_lane_2019, title={A data-driven approach to scale bridging in system thermal-hydraulic simulation}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85073761938&partnerID=MN8TOARS}, booktitle={18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2019}, author={Bao, H. and Youngblood, R. and Zhang, H. and Dinh, N. and Lin, L. and Lane, J.}, year={2019}, pages={6069–6082} }
 @article{bao_dinh_lane_youngblood_2019, title={A data-driven framework for error estimation and mesh-model optimization in system-level thermal-hydraulic simulation}, volume={349}, ISSN={["1872-759X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85064505536&partnerID=MN8TOARS}, DOI={10.1016/j.nucengdes.2019.04.023}, abstractNote={Over the past decades, several computer codes have been developed for simulation and analysis of thermal-hydraulics and system response in nuclear reactors under operating, abnormal transient, and accident conditions. However, simulation errors and uncertainties still inevitably exist even while these codes have been extensively assessed and used. In this work, a data-driven framework (Optimal Mesh/Model Information System, OMIS) is formulated and demonstrated to estimate simulation error and suggest optimal selection of computational mesh size (i.e., nodalization) and constitutive correlations (e.g., wall functions and turbulence models) for low-fidelity, coarse-mesh thermal-hydraulic simulation, in order to achieve accuracy comparable to that of high-fidelity simulation. Using results from high-fidelity simulations and experimental data with many fast-running low-fidelity simulations, an error database is built and used to train a machine learning model that can determine the relationship between local simulation error and local physical features. This machine learning model is then used to generate insight and help correct low-fidelity simulations for similar physical conditions. The OMIS framework is designed as a modularized six-step procedure and accomplished with state-of-the-art methods and algorithms. A mixed-convection case study was performed to illustrate the entire framework.}, journal={NUCLEAR ENGINEERING AND DESIGN}, author={Bao, Han and Dinh, Nam T. and Lane, Jeffrey W. and Youngblood, Robert W.}, year={2019}, month={Aug}, pages={27–45} }
 @article{athe_dinh_2019, title={A framework for assessment of predictive capability maturity and its application in nuclear thermal hydraulics}, volume={354}, ISSN={["1872-759X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85070311923&partnerID=MN8TOARS}, DOI={10.1016/j.nucengdes.2019.110201}, abstractNote={This work presents a formalized and computerized framework for the assessment of decision regarding the adequacy of a simulation tool for a nuclear reactor application. The decision regarding a code’s adequacy for an application is dependent on the assessment of different attributes that govern verification, validation, and uncertainty quantification of the code. In this work, the focus is on code validation. Therefore, the framework is developed and illustrated from the perspective of decision regarding the validation assessment of a code. Code validation assessment is performed based on the validation test results, data applicability, and process quality assurance factors. The process quality assurance factors warrant the trustworthiness of the evidence and help in checking people and process compliance with respect to the standard requirements. The proposed framework is developed using an argument modeling technique called Goal Structuring Notation (GSN). Goal structuring notation facilitates structural knowledge representation, information abstraction, evidence incorporation, and provides a skeletal structure for quantitative maturity assessment. The decision schema for the development of the decision model is based on the Predictive Capability Maturity Model (PCMM) and Analytic Hierarchy Process (AHP) and formalized using Goal structuring notation. Each decision attribute is formulated as a claim, where the degree of validity of the claim (attribute’s assessment) is expressed using different maturity levels. The GSN representation of the decision model is transformed into a confidence network to provide evidence-based quantitative maturity assessment using the Bayesian network. A metric based on the expected utility of maturity levels, called expected distance metric, is proposed to measure the distance between target maturity and achieved maturity on a scale of zero to one. Expected distance metric helps in comparing the assessment of different attributes and identification of major areas of concern in terms of modeling capability, data needs, and quality of assessment process. The practical application of the framework is demonstrated by a case study on validation assessment of a thermal-hydraulic code for a challenge problem called Departure from Nucleate Boiling (DNB).}, journal={NUCLEAR ENGINEERING AND DESIGN}, publisher={Elsevier BV}, author={Athe, Paridhi and Dinh, Nam}, year={2019}, month={Dec} }
 @inproceedings{hanna_son_dinh_2019, title={An artificial intelligence-guided decision support system for the nuclear power plant management}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85073712176&partnerID=MN8TOARS}, booktitle={18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2019}, author={Hanna, B. and Son, T.C. and Dinh, N.}, year={2019}, pages={394–406} }
 @inproceedings{lin_dinh_prescott_bao_montanari_sampath_2019, title={Assessment of smoothed particle hydrodynamics methods for simulating the external-flooding scenario}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85073736251&partnerID=MN8TOARS}, booktitle={18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2019}, author={Lin, L. and Dinh, N. and Prescott, S. and Bao, H. and Montanari, N. and Sampath, R.}, year={2019}, pages={981–992} }
 @article{chang_dinh_2019, title={Classification of machine learning frameworks for data-driven thermal fluid models}, volume={135}, ISSN={["1778-4166"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85054594382&partnerID=MN8TOARS}, DOI={10.1016/j.ijthermalsci.2018.09.002}, abstractNote={Thermal fluid processes are inherently multi-physics and multi-scale, involving mass-momentum-energy transport phenomena. Thermal fluid simulation (TFS) is based on solving conservative equations, for which - except for "first-principle" direct numerical simulation - closure relations (CRs) are required to provide microscopic interactions. In practice, TFS is realized through reduced-order modeling, and its CRs can be informed by observations and data from relevant and adequately evaluated experiments and high-fidelity simulations. This paper focuses on data-driven TFS models, specifically on the development using machine learning (ML). Five ML frameworks, dubbed Type I to V, are introduced. The frameworks vary in their performance for different applications depending on the level of knowledge of governing physics, the source, type, amount and quality of available data for training. Notably, outlined for the first time in this paper, Type III models present stringent requirements on modeling, substantial computing resources for training, and high potential in extracting value from "big data" in thermal fluid research. The paper demonstrates the ML frameworks by three examples. First, we utilize the heat diffusion equation with nonlinear conductivity formulated by convolutional neural networks to illustrate the applications of Type I, II, and III ML. The results indicate a preference for Type II ML under deficient data support. Type III ML can effectively utilize field data, potentially generating more robust predictions than Type I and II ML. Second, we illustrate how to employ Type I ML and Type II ML frameworks for data-driven turbulence modeling using reference works. Third, we demonstrate Type I ML by building a deep learning (DL)-based slip closure for two-phase flow modeling. The results showe that the DL-based closure exhibits a bounded error in prediction domain.}, journal={INTERNATIONAL JOURNAL OF THERMAL SCIENCES}, author={Chang, Chih-Wei and Dinh, Nam T.}, year={2019}, month={Jan}, pages={559–579} }
 @inproceedings{bao_feng_zhang_dinh_2019, title={Demonstration of a data-driven approach for error estimation in two-phase flow simulation using coarse-mesh CFD}, volume={121}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85092125933&partnerID=MN8TOARS}, DOI={10.13182/31051}, booktitle={Transactions of the American Nuclear Society}, author={Bao, H. and Feng, J. and Zhang, H. and Dinh, N.}, year={2019}, pages={1865–1868} }
 @inproceedings{zhu_dinh_hu_kraus_2019, title={Development of a data-driven turbulence model for 3D thermal stratification simulation during reactor transients}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85073734574&partnerID=MN8TOARS}, booktitle={18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2019}, author={Zhu, Y. and Dinh, N. and Hu, R. and Kraus, A.}, year={2019}, pages={2223–2234} }
 @inproceedings{chang_fang_dinh_2019, title={Reynolds-averaged turbulence modeling using deep learning with local flow features}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85073713566&partnerID=MN8TOARS}, booktitle={18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2019}, author={Chang, C.-W. and Fang, J. and Dinh, N.T.}, year={2019}, pages={1698–1711} }
 @article{aksan_andreani_bechta_corradini_d’auria_dhir_frid_jones_jong_lillington_et al._2019, title={The life and the contribution of B. R. Sehgal, G. Yadigaroglu and G. Hewitt: Remembrance statements}, volume={354}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85070500941&partnerID=MN8TOARS}, DOI={10.1016/j.nucengdes.2019.110252}, abstractNote={Solicited or voluntary statements have been collected by the Editor of the Special Issue (SI). Tributes to Sehgal, Yadigaroglu and Hewitt are reported in the alphabetical order of those who originated them. The concise tributes by N. Todreas related to all the three scientists constitute the paper PII-1 in this SI and are also reported hereafter. Romney Duffey and John Jones wrote dedicated tributes with scientific insights which constitute PII-7 and PII-8 in this SI. A number of others helped with biographies of Sehgal, Yadigaroglu and Hewitt and are acknowledged in paper PII-2.}, journal={Nuclear Engineering and Design}, author={Aksan, N. and Andreani, M. and Bechta, S. and Corradini, M. and D’Auria, F. and Dhir, V. and Frid, W. and Jones, J. and Jong, K. and Lillington, J. and et al.}, year={2019} }
 @inproceedings{liu_sun_liu_dinh_2019, title={Uncertainty quantification and reduction for multiphase-CFD solvers: A data-driven Bayesian approach supported by high-resolution local measurements}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85073755203&partnerID=MN8TOARS}, booktitle={18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2019}, author={Liu, Y. and Sun, X. and Liu, Y. and Dinh, N.}, year={2019}, pages={3582–3597} }
 @article{liu_dinh_smith_sun_2019, title={Uncertainty quantification of two-phase flow and boiling heat transfer simulations through a data-driven modular Bayesian approach}, volume={138}, ISSN={["1879-2189"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85064892196&partnerID=MN8TOARS}, DOI={10.1016/j.ijheatmasstransfer.2019.04.075}, abstractNote={In this paper, we present an approach to inversely quantify the uncertainty of MCFD simulations through a data-driven modular Bayesian inference. Both the model parameter uncertainty and the model form uncertainty are evaluated in the proposed approach. Considering the high-dimensionality of parameter space related to the solver, we performed a sensitivity analysis to reduce the input parameter dimension for the Bayesian inference. Based on the reduced parameter dimension, surrogate models based on Gaussian Process (GP) and Principal Component Analysis (PCA) are constructed to reduce the computational cost in the Bayesian inference. Two case studies based on the proposed approach are performed, focusing on two-phase flow dynamics and on wall boiling heat transfer, respectively. In case study I, we are able to construct a GP-based surrogate model based on 8 principal components to represent the total 208 MCFD solver outputs. Moreover, both cases show that the proposed approach is able to quantify and reduce the parameter uncertainties with the support of experimental measurements. The posterior uncertainties of investigated parameters have 50%-90% narrowed uncertainty ranges compared to their prior uncertainties. Furthermore, a forward uncertainty propagation of the MCFD solver with the obtained uncertainties shows that the agreement between the solver predictions and experimental measurements are significantly improved.}, journal={INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER}, author={Liu, Yang and Dinh, Nam T. and Smith, Ralph C. and Sun, Xiaodong}, year={2019}, month={Aug}, pages={1096–1116} }
 @article{liu_sun_dinh_2019, title={Validation and uncertainty quantification of multiphase-CFD solvers: A data-driven Bayesian framework supported by high-resolution experiments}, volume={354}, ISSN={["1872-759X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85069632428&partnerID=MN8TOARS}, DOI={10.1016/j.nucengdes.2019.110200}, abstractNote={The two-fluid model-based Multiphase Computational Fluid Dynamics (MCFD) solvers are promising tools for a variety of engineering problems related to multiphase flows. Such a solver is a complex model system that consists of multiple closure relations with strong interactions. Furthermore, a typical engineering problem requires evaluation of multiple quantities of interest (QoIs) from the solver predictions. These features make the validation and uncertainty quantification (VUQ) of these MCFD solvers a challenging task. In this paper, we propose an approach for the VUQ of a two-fluid model-based MCFD solver based on a data-driven Bayesian framework. This framework relies on Bayesian inference to inversely quantify the parameter uncertainty and model form uncertainty and then propagate the obtained uncertainties through the solver to obtain the uncertainties of the QoI predictions. To make the Bayesian inference applicable to complicated MCFD simulations, two methods namely, parameter space reduction and surrogate modeling, are included in the proposed approach. Supported by high-resolution local measurements, this framework is able to simultaneously take multiple key QoIs into consideration. In the validation process, the area metric is extended to the Principal Component (PC) subspace so that the multiple correlated QoIs, in the form of spatial or temporal distributions, can be validated in a comprehensive manner. We demonstrate the applicability of the proposed approach with a case study of an adiabatic bubbly flow scenario.}, journal={NUCLEAR ENGINEERING AND DESIGN}, author={Liu, Yang and Sun, Xiaodong and Dinh, Nam T.}, year={2019}, month={Dec} }
 @inproceedings{hanna_dinh_bolotnov_2018, title={Coarse grid computational fluid dynamics (cg-cfd) error prediction via random forest regression}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85050164371&partnerID=MN8TOARS}, booktitle={Proceedings of the 2018 International Congress on Advances in Nuclear Power Plants, ICAPP 2018}, author={Hanna, B.N. and Dinh, N. and Bolotnov, I.A.}, year={2018}, pages={1125–1133} }
 @article{liu_dinh_sato_niceno_2018, title={Data-driven modeling for boiling heat transfer: Using deep neural networks and high-fidelity simulation results}, volume={144}, ISSN={["1873-5606"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85051950117&partnerID=MN8TOARS}, DOI={10.1016/j.applthermaleng.2018.08.041}, abstractNote={Boiling heat transfer occurs in many situations and can be used for thermal management in various engineered systems with high energy density, from power electronics to heat exchangers in power plants and nuclear reactors. Essentially, boiling is a complex physical process that involves interactions between heating surface, liquid, and vapor. For engineering applications, the boiling heat transfer is usually predicted by empirical correlations or semi-empirical models, which has relatively large uncertainty. In this paper, a data-driven approach based on deep feedforward neural networks is studied. The proposed networks use near wall local features to predict the boiling heat transfer. The inputs of networks include the local momentum and energy convective transport, pressure gradients, turbulent viscosity, and surface information. The outputs of the networks are the quantities of interest of a typical boiling system, including heat transfer components, wall superheat, and near wall void fraction. The networks are trained by the high-fidelity data processed from first principle simulation of pool boiling under varying input heat fluxes. State-of-the-art algorithms are applied to prevent the overfitting issue when training the deep networks. The trained networks are tested in interpolation cases and extrapolation cases which both demonstrate good agreement with the original high-fidelity simulation results.}, journal={APPLIED THERMAL ENGINEERING}, author={Liu, Yang and Dinh, Nam and Sato, Yohei and Niceno, Bojan}, year={2018}, month={Nov}, pages={305–320} }
 @inproceedings{zhang_liu_sun_dinh_2018, title={Design of validation experiments for model improvement of dispersed flow film boiling in COBRA-TF}, volume={119}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85060849109&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Zhang, X. and Liu, Y. and Sun, X. and Dinh, N.}, year={2018}, pages={133–136} }
 @article{lei_zhang_zhang_dinh_li_2018, title={Experimental investigations on the boiling heat transfer of horizontal flow in the near-critical region}, volume={125}, ISSN={["1879-2189"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85046342995&partnerID=MN8TOARS}, DOI={10.1016/j.ijheatmasstransfer.2018.04.043}, abstractNote={The critical point is the end point of a phase equilibrium curve; liquid and its vapor can coexist under designated points. Close to the critical point, thermophysical properties present clear variations, especially in the region of 0.85Pcr∼Pcr. Latent heat and liquid density in this region decrease more quickly than in lower-pressure areas, resulting in unique boiling heat transfer behavior. This region is also called the near-critical region. However, only a few scholars have discussed the heat transfer phenomenon; thus, it is difficult to ascertain the near-critical region’s properties and characteristics from extant literature. In the present study, we conduct experimental investigations to explore the specificities of the heat transfer characteristics of carbon dioxide in horizontal flow within the near-critical region in a circular channel with a diameter of 4 mm. The operating pressure ranges from 6.26 MPa to 7.3 MPa with a mass flow rate between 200 and 400 kg/m2 s, heat flux between 5 and 140 kW/m2, and test section inlet temperature of −5 °C. Then, we examine the inner-wall temperature and heat transfer coefficient profiles at different pressures within the near-critical region. The results show that at high heat flux, departure from nucleate boiling (DNB) phenomenon presents with a sudden decrease in the heat transfer coefficient in the subcooled region. The higher the heat flux, the more seriously deteriorating the heat transfer is. Interestingly, the temperature reaches its peak in the post-DNB region rather than at the critical vapor quality point. With an increase in pressure, DNB occurs early with lower vapor quality, and the temperature peak decreases at the given heat flux and mass flux. On the contrary, DNB is delayed with an increase in mass flux. A series of boiling heat transfer correlations in a subcooled region, two-phase flow region, and superheated region are proposed in addition to a new predictive correlation for critical heat flux in the near-critical region at a given mass flux.}, journal={INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER}, author={Lei, Xianliang and Zhang, Weiqiang and Zhang, Jun and Dinh, Nam and Li, Huixiong}, year={2018}, month={Oct}, pages={618–628} }
 @book{liu_dinh_2018, title={Flow boiling in tubes}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85063117927&partnerID=MN8TOARS}, DOI={10.1007/978-3-319-26695-4_47}, journal={Handbook of Thermal Science and Engineering}, author={Liu, Y. and Dinh, N.}, year={2018}, pages={1907–1949} }
 @inproceedings{liu_shi_qian_sun_dinh_2018, title={Inverse uncertainty quantification of turbulence modeling in multiphase-CFD solver using high-resolution data from particle image velocimetry}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85060164897&partnerID=MN8TOARS}, booktitle={International Topical Meeting on Advances in Thermal Hydraulics, ATH 2018 - Embedded Topical Meeting}, author={Liu, Y. and Shi, S. and Qian, Y. and Sun, X. and Dinh, N.}, year={2018}, pages={1028–1040} }
 @inproceedings{lin_dinh_2018, title={Predictive capability and maturity assessment with Bayesian network}, volume={118}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85063015132&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Lin, L. and Dinh, N.}, year={2018}, pages={1087–1090} }
 @article{kwag_gupta_dinh_2018, title={Probabilistic risk assessment based model validation method using Bayesian network}, volume={169}, ISSN={["1879-0836"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85030567554&partnerID=MN8TOARS}, DOI={10.1016/j.ress.2017.09.013}, abstractNote={Past few decades have seen a rapid growth in the availability of computational power and that induces continually reducing cost of simulation. This rapidly changing scenario together with availability of high precision and large-scale experimental data has enabled development of high fidelity simulation tools capable of simulating multi-physics multi-scale phenomena. At the same time, there has been an increased emphasis on developing strategies for verification and validation of such high fidelity simulation tools. The problem is more pronounced in cases where it is not possible to collect experimental data or field measurements on a large-scale or full scale system performance. This is particularly true in case of systems such as nuclear power plants subjected to external hazards such as earthquakes or flooding. In such cases, engineers rely solely on simulation tools but struggle to establish the credibility of the system level simulations. In practice, validation approaches rely heavily on expert elicitation. There is an increasing need of a quantitative approach for validation of high fidelity simulations that is comprehensive, consistent, and effective. A validation approach should be able to consider uncertainties due to incomplete knowledge and randomness in the system's performance as well as in the characterization of external hazard. A new approach to validation is presented in this paper that uses a probabilistic index as a degree of validation and propagates it through the system using the performance-based probabilistic risk assessment (PRA) framework. Unlike traditional PRA approaches, it utilizes the power of Bayesian statistic to account for non-Boolean relationships and correlations among events at various levels of a network representation of the system. Bayesian updating facilitates evaluation of updated validation information as additional data from experimental observations or improved simulations is incorporated. PRA based framework assists in identifying risk-consistent events and critical path for appropriate allocation of resources to improve the validation.}, journal={RELIABILITY ENGINEERING & SYSTEM SAFETY}, author={Kwag, Shinyoung and Gupta, Abhinav and Dinh, Nam}, year={2018}, month={Jan}, pages={380–393} }
 @article{bao_zhao_zhang_zou_sharpe_dinh_2018, title={Safe reactor depressurization windows for BWR Mark I Station Blackout accident management strategy}, volume={114}, ISSN={["0306-4549"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85043374484&partnerID=MN8TOARS}, DOI={10.1016/j.anucene.2017.12.063}, abstractNote={In order to evaluate the effectiveness of reactor depressurization within accident mitigation strategy and how to avoid core damage during Station Black-Out accident in a BWR Mark I plant, a GOTHIC model has been developed to support characterization of reactor safety systems performance. The GOTHIC model provides seamless coupled simulations of the reactor coolant system and the containment system. In this study, the time intervals (also called “safe reactor depressurization windows”) to initiate the reactor depressurization in order to optimize the early cooling strategy by injecting fire water and avoid clad failure are studied based on the decay heat removal capability of the reactor vessel coolant. This concept is instructive for the operation of the safety systems during the SBO accident mitigation. Sensitivity studies of several key parameters like reactor power, mass flow rates through RCIC system and fire water injection, and full open discharge coefficient of SRVs are performed to evaluate their impact on the safe reactor depressurization windows.}, journal={ANNALS OF NUCLEAR ENERGY}, author={Bao, Han and Zhao, Haihua and Zhang, Hongbin and Zou, Ling and Sharpe, Phil and Dinh, Nam}, year={2018}, month={Apr}, pages={518–529} }
 @inproceedings{bao_dinh_lane_youngblood_2018, title={Study of data-driven mesh-model optimization in system thermal-hydraulic simulation}, volume={118}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85062961048&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Bao, H. and Dinh, N. and Lane, J. and Youngblood, R.}, year={2018}, pages={1091–1094} }
 @article{liu_dinh_2018, title={Validation and Uncertainty Quantification for Wall Boiling Closure Relations in Multiphase-CFD Solver}, volume={193}, ISSN={0029-5639 1943-748X}, url={http://dx.doi.org/10.1080/00295639.2018.1512790}, DOI={10.1080/00295639.2018.1512790}, abstractNote={Abstract Two-fluid model-based multiphase computational fluid dynamics (MCFD) has been considered one of the most promising tools to investigate a two-phase flow and boiling system for engineering purposes. The MCFD solver requires closure relations to make the conservation equations solvable. The wall boiling closure relations, for example, provide predictions on wall superheat and heat partitioning. The accuracy of these closure relations significantly influences the predictive capability of the solver. In this paper, a study of validation and uncertainty quantification (VUQ) for the wall boiling closure relations in the MCFD solver is performed. The work has three purposes: (1) to identify influential parameters to the quantities of interest (QoIs) of the boiling system through sensitivity analysis (SA), (2) to evaluate the parameter uncertainty through Bayesian inference with the support of multiple data sets, and (3) to quantitatively measure the agreement between solver predictions and data sets. The widely used Kurul-Podowski wall boiling closure relation is studied in this paper. Several statistical methods are used, including the Morris Screening method for global SA, Markov Chain Monte Carlo for inverse Bayesian inference, and confidence interval as the validation metric. The VUQ results indicate that the current empirical correlations-based wall boiling closure relations achieved satisfactory agreement on wall superheat predictions. However, the closure relations also demonstrate intrinsic inconsistency and fail to give consistently accurate predictions for all QoIs over the well-developed nucleate boiling regime.}, number={1-2}, journal={Nuclear Science and Engineering}, publisher={Informa UK Limited}, author={Liu, Yang and Dinh, Nam}, year={2018}, month={Sep}, pages={81–99} }
 @inproceedings{zhu_dinh_2017, title={A data-driven approach for turbulence modeling}, volume={2017-September}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85052541047&partnerID=MN8TOARS}, booktitle={17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017}, author={Zhu, Y. and Dinh, N.}, year={2017} }
 @article{lei_li_dinh_zhang_2017, title={A study of heat transfer scaling of supercritical pressure water in horizontal tubes}, volume={114}, ISSN={["1879-2189"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85021702180&partnerID=MN8TOARS}, DOI={10.1016/j.ijheatmasstransfer.2017.06.052}, abstractNote={Understanding the role of the heat transfer scaling in supercritical utilities can help us obtain a better design for supercritical single phase thermosiphons. In this paper, heat transfer scaling analysis of supercritical pressure water in horizontal tubes with differential inside diameters are experimentally investigated. The operating conditions included mass flux of 100–600 kg/m2 s and heat flux of up to 400 kW/m2. The uneven circumferential temperature distributions are discussed firstly over a broad range of heat fluxes. A significant temperature discrepancy exists between the top and bottom surface in each pipe, deteriorated heat transfer occurs on the top surface but enhanced heat transfer happens in the bottom region. With the rise of heat flux, more severe deterioration appears on the higher domain. Then a qualitatively comparison on the heat transfer characteristic of supercritical flow in different pipes are implemented. Evidently, with the increase of tube diameter, the inner-wall temperature peak is much pronounced and the degree of deterioration at the top surface much severe due to the intensification of buoyancy force. The heat transfer mechanism of horizontal pipes is further discussed by comparing the effect of buoyancy and thermal acceleration. With the augment of diameter, free convection gradually intensifies due to its steeper density variation and expanded flow space, which leads to larger temperature deviation between the bottom and top region along the circumferential direction. On the contrary, thermal acceleration plays a relatively minor role in deteriorated heat transfer. Considering the scaling effect in various pipes, two heat transfer correlations are proposed respectively in both the bottom and top region of the horizontal flows.}, journal={INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER}, author={Lei, Xianliang and Li, Huixiong and Dinh, Nam and Zhang, Weiqiang}, year={2017}, month={Nov}, pages={923–933} }
 @inproceedings{lin_dinh_montanari_sampath_akinci_prescott_2017, title={Assessment of smoothed particle hydrodynamics in application of high-wind risk analysis}, volume={2017-September}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85047791478&partnerID=MN8TOARS}, booktitle={17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017}, author={Lin, L. and Dinh, N. and Montanari, N. and Sampath, R. and Akinci, N. and Prescott, S.}, year={2017} }
 @inproceedings{liu_dinh_2017, title={Development of a VUQ framework for Wall Boiling model in McFD Solver}, volume={2017-September}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85052384281&partnerID=MN8TOARS}, booktitle={17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017}, author={Liu, Y. and Dinh, N.}, year={2017} }
 @article{lei_li_zhang_dinh_guo_yu_2017, title={Experimental study on the difference of heat transfer characteristics between vertical and horizontal flows of supercritical pressure water}, volume={113}, ISSN={["1359-4311"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84995775922&partnerID=MN8TOARS}, DOI={10.1016/j.applthermaleng.2016.11.051}, abstractNote={The present paper is devoted to investigating the difference of heat transfer characteristics between horizontal and vertical upward flows of supercritical pressure water. An Experimental study is conducted with both horizontal and vertical upward tubes (∅32 mm × 3 mm), covering a range of mass fluxes (G) from 200 to 600 kg·m−2·s−1, heat fluxes (q) up to 400 kW·m−2, and pressure (P) from 23 to 28 MPa. Heat transfer characteristics are analyzed in detail for selected parameters. The results show at low q/G, an apparent heat transfer enhancement and insignificant difference in the two arrangements. However, when the q/G increases to a higher value (i.e. q/G > 0.5), heat transfer deterioration occurs and a noticeable heat transfer discrepancy is detected, where the inner-wall temperature of vertical flow far exceeds that of horizontal flow. Dimensionless parameters, Bo+, Kν, and BTH are adopted to analyze the effects of buoyancy force and thermal acceleration for both flows. The analysis suggests that mechanisms governing horizontal and vertical flows of supercritical pressure water are different at high q/G or in deteriorated heat transfer mode. For the vertical flow, thermal acceleration plays a leading role, while for the horizontal flow, the effect of buoyancy plays a larger effect than that for vertical flow.}, journal={APPLIED THERMAL ENGINEERING}, author={Lei, Xianliang and Li, Huixiong and Zhang, Weiqiang and Dinh, Nam T. and Guo, Yumeng and Yu, Shuiqing}, year={2017}, month={Feb}, pages={609–620} }
 @inproceedings{hess_prescott_smith_lin_dinh_sampath_montanari_2017, title={Integrated use of modeling and simulation in high winds PRA}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85047784184&partnerID=MN8TOARS}, booktitle={International Topical Meeting on Probabilistic Safety Assessment and Analysis, PSA 2017}, author={Hess, S.M. and Prescott, S. and Smith, C. and Lin, L. and Dinh, N. and Sampath, R. and Montanari, N.}, year={2017}, pages={30–39} }
 @inproceedings{chang_dinh_cetiner_2017, title={Physics-constrained machine learning for two-phase flow simulation using deep learning-based closure relation}, volume={117}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85054585553&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Chang, C.-W. and Dinh, N. and Cetiner, S.M.}, year={2017}, pages={1749–1752} }
 @inproceedings{liu_rollins_dinh_luo_2017, title={Sensitivity analysis of interfacial momentum closure terms in two phase flow and boiling simulations using MCFD solver}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85032902821&partnerID=MN8TOARS}, DOI={10.1115/ht2017-4963}, abstractNote={In this paper, a general workflow for the global Sensitivity Analysis (SA) has been proposed based on the coupling of VUQ toolkit DAKOTA and Multiphase Computational Fluid Dynamics (MCFD) solver boilEulerFoam. A surrogate model is first constructed based on sampling simulations from boilEulerFoam. This surrogate is based on Gaussian Processes Model (GPM) and is validated and proved to have good properties. The Morris Screening method is then applied based on the surrogate to those interfacial momentum closure terms for SA, including drag, lift, turbulent dispersion, wall lubrication, and virtual mass. Two different cases are considered, one is on low-pressure adiabatic flow, and the other is on high pressure boiling flow. Each case has its experimental background with data support. The radial void fraction distribution, gas velocity, relative velocity and liquid temperature (only for high pressure boiling case) are chosen as the Quantities of Interest (QoIs) which are of key interests for two-phase flow simulation and boiling crisis prediction. The interfacial force coefficient of each closure term is chosen as the input parameter. For the boiling case, the bubble diameter effect is also analyzed.}, booktitle={ASME 2017 Heat Transfer Summer Conference, HT 2017}, author={Liu, Y. and Rollins, C. and Dinh, Nam and Luo, H.}, year={2017} }
 @inproceedings{lin_dinh_sampath_akinci_2016, title={A computational study of thin film dynamics on micro-structured surfaces}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85002986155&partnerID=MN8TOARS}, DOI={10.1115/HT2016-7382}, abstractNote={The present study is motivated by interest in understanding of physical mechanisms that govern the effect of material and micro-structural characteristics of heat surface on boiling heat transfer and burnout at high heat fluxes. The effect was reported and investigated experimentally and analytically over several past decades. Only recently, with the advent of nanotechnology including microscale manufacturing, it becomes possible to perform high heat-flux boiling experiments with control of surface conditions.}, booktitle={ASME 2016 Heat Transfer Summer Conference, HT 2016, collocated with the ASME 2016 Fluids Engineering Division Summer Meeting and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels}, author={Lin, L. Y. and Dinh, N. T. and Sampath, R. and Akinci, N.}, year={2016} }
 @inproceedings{bao_dinh_omotowa_zhao_zhang_zou_szilard_2016, title={A study of bwr mark i station blackout accident with GOTHIC modeling}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84986182404&partnerID=MN8TOARS}, booktitle={International Congress on Advances in Nuclear Power Plants, ICAPP 2016}, author={Bao, H. and Dinh, N. and Omotowa, O. and Zhao, H. and Zhang, H. and Zou, L. and Szilard, R.H.}, year={2016}, pages={184–193} }
 @inproceedings{chang_dinh_2016, title={A study of physics-informed deep learning for system fluid dynamics closures}, volume={115}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85033222005&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Chang, C.-W. and Dinh, N.}, year={2016}, pages={1785–1788} }
 @article{liu_dinh_2016, title={Analysis of heat transfer under high heat flux nucleate boiling conditions}, volume={81}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85017625515&partnerID=MN8TOARS}, DOI={10.3139/124.110750}, abstractNote={Abstract}, number={3}, journal={Kerntechnik}, author={Liu, Y. and Dinh, N.}, year={2016}, pages={308–314} }
 @inproceedings{lin_dinh_2016, title={Assessment of a smoothed particle hydrodynamics method for thin film on textured surfaces}, volume={115}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85033230091&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Lin, L. and Dinh, N.}, year={2016}, pages={1453–1456} }
 @inproceedings{lee_dinh_son_2016, title={Development of a severe accident analysis engine using approximate reasoning}, volume={115}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85032884451&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Lee, J. and Dinh, N. and Son, T.C.}, year={2016}, pages={830–833} }
 @article{corradini_dinh_leon_2016, title={Foreword special issue on the 16th international topical meeting on nuclear reactor thermal hydraulics}, volume={184}, number={3}, journal={Nuclear Science and Engineering}, author={Corradini, M. and Dinh, N. T. and Leon, S. B. Y.}, year={2016}, pages={III-} }
 @inproceedings{hanna_dinh_bolotnov_2016, title={High-fidelity simulation-driven model development for coarse-grained computational fluid dynamics}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84992089403&partnerID=MN8TOARS}, booktitle={International Topical Meeting on Advances in Thermal Hydraulics 2016, ATH 2016}, author={Hanna, B.N. and Dinh, N.T. and Bolotnov, I.A.}, year={2016}, pages={121–131} }
 @inproceedings{athe_dinh_abdel-khalik_2016, title={Investigation of similarity metrics for simulation based scaling analysis}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84992126794&partnerID=MN8TOARS}, booktitle={International Topical Meeting on Advances in Thermal Hydraulics 2016, ATH 2016}, author={Athe, P. and Dinh, N. and Abdel-Khalik, H.}, year={2016}, pages={409–425} }
 @inproceedings{dinh_no_sun_leon_merzari_pointer_2015, title={Foreword}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84962754306&partnerID=MN8TOARS}, booktitle={International Topical Meeting on Nuclear Reactor Thermal Hydraulics 2015, NURETH 2015}, author={Dinh, N. and No, H.C. and Sun, X. and Leon, S.B.Y. and Merzari, E. and Pointer, W.D.}, year={2015} }
 @inproceedings{bao_zhao_zhang_zou_szilard_dinh_2015, title={Simulation of BWR Mark i station black-out accident using GOTHIc: An initial demonstration}, volume={113}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85043354152&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Bao, H. and Zhao, H. and Zhang, H. and Zou, L. and Szilard, R.H. and Dinh, N.}, year={2015}, pages={1377–1380} }
 @inproceedings{liu_dinh_2015, title={Treatment of nucleation and bubble dynamics in high heat flux film boiling}, volume={5}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84962715457&partnerID=MN8TOARS}, booktitle={International Topical Meeting on Nuclear Reactor Thermal Hydraulics 2015, NURETH 2015}, author={Liu, Y. and Dinh, N.}, year={2015}, pages={4097–4111} }
 @inproceedings{kudinov_galushin_yakush_villanueva_phung_grishchenko_dinh_2014, title={A framework for assessment of severe accident management effectiveness in Nordic BWR plants}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85066711344&partnerID=MN8TOARS}, booktitle={PSAM 2014 - Probabilistic Safety Assessment and Management}, author={Kudinov, P. and Galushin, S. and Yakush, S. and Villanueva, W. and Phung, V.-A. and Grishchenko, D. and Dinh, N.}, year={2014} }
 @inproceedings{chang_dinh_2014, title={A scoping study of direct containment heating in a small modular reactor}, volume={111}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84939132697&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Chang, C.-W. and Dinh, N.}, year={2014}, pages={907–910} }
 @inproceedings{bui_williams_dinh_2014, title={Advanced calibration and validation of a mechanistic model of subcooled boiling two-phase flow}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84907072042&partnerID=MN8TOARS}, booktitle={International Congress on Advances in Nuclear Power Plants, ICAPP 2014}, author={Bui, A. and Williams, B. and Dinh, N.}, year={2014}, pages={1486–1493} }
 @inproceedings{hanna_dinh_bolotnov_2014, title={Development of 3D containment simulation capability: High pressure steam slowdown scenario}, volume={111}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84939153178&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Hanna, B. and Dinh, N. and Bolotnov, I.}, year={2014}, pages={1545–1548} }
 @inproceedings{dinh_ren_lee_2014, title={Validation data: Managing the weak link}, volume={111}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84939158259&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Dinh, N. and Ren, W. and Lee, H.}, year={2014}, pages={1444–1445} }
 @article{hansson_dinh_manickam_2013, title={A study of the effect of binary oxide materials in a single droplet vapor explosion}, volume={264}, ISSN={0029-5493}, url={http://dx.doi.org/10.1016/J.NUCENGDES.2013.02.017}, DOI={10.1016/j.nucengdes.2013.02.017}, abstractNote={In an effort to explore fundamental mechanisms that may govern the effect of melt material on vapor explosion's triggering, fine fragmentation and energetics, a series of experiments using a binary-oxide mixture with eutectic and non-eutectic compositions were performed. Interactions of a hot liquid (WO3–CaO) droplet and a volatile liquid (water) were investigated in well-controlled, externally triggered, single-droplet experiments conducted in the Micro-interactions in steam explosion experiments (MISTEE) facility. The tests were visualized by means of a synchronized digital cinematography and continuous X-ray radiography system, called simultaneous high-speed acquisition of X-ray radiography and photography (SHARP). The acquired images followed by further analysis indicate milder interactions for the droplet with non-eutectic melt composition in the tests with low melt superheat, whereas no evident differences between eutectic and non-eutectic melt compositions regarding bubble dynamics, energetics and melt preconditioning was observed in the tests with higher melt superheat.}, journal={Nuclear Engineering and Design}, publisher={Elsevier BV}, author={Hansson, R.C. and Dinh, T.N. and Manickam, L.T.}, year={2013}, month={Nov}, pages={168–175} }
 @article{dinh_2013, title={Guest editorial special issue on “Nuclear reactor safety simulation and uncertainty analysis”}, volume={52}, ISSN={0306-4549}, url={http://dx.doi.org/10.1016/j.anucene.2012.11.013}, DOI={10.1016/j.anucene.2012.11.013}, journal={Annals of Nuclear Energy}, publisher={Elsevier BV}, author={Dinh, Truc-Nam}, year={2013}, month={Feb}, pages={1} }
 @inproceedings{dinh_tu_2013, title={Observations of bubble nucleation and interaction dynamics in high heat flux boiling}, volume={109}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84902837363&partnerID=MN8TOARS}, number={PART 2}, booktitle={Transactions of the American Nuclear Society}, author={Dinh, T.-N. and Tu, J.P.}, year={2013}, pages={1819–1820} }
 @inproceedings{bui_dinh_nourgaliev_williams_2013, title={Statistical modeling support for calibration of a multiphysics model of subcooled boiling flows}, volume={3}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84883314135&partnerID=MN8TOARS}, booktitle={International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M and C 2013}, author={Bui, A.V. and Dinh, N.T. and Nourgaliev, R.R. and Williams, B.J.}, year={2013}, pages={2229–2244} }
 @article{gong_ma_dinh_2012, title={Simulation and validation of the dynamics of liquid films evaporating on horizontal heater surfaces}, volume={48}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84863494032&partnerID=MN8TOARS}, DOI={10.1016/j.applthermaleng.2012.05.021}, abstractNote={In this study a non-linear governing equation based on lubrication theory is employed to model the thinning process of an evaporating liquid film and ultimately predict the critical thickness of the film rupture under impacts of various forces resulting from mass loss, surface tension, gravity, vapor recoil and thermo-capillary. It is found that the thinning process in the experiment is well reproduced by the simulation. The film rupture is caught by the simulation as well, but it underestimates the measured critical thickness at the film rupture. The reason may be that the water wettability of the heater surfaces is not taken into account in the model. Thus, the minimum free energy criterion is used to obtain a correlation which combines the contact angle (reflection of wettability) with the critical thickness from the simulation. The critical thicknesses predicted by the correlation have a good agreement with the experimental data (the maximum deviation is less than 10%).}, journal={Applied Thermal Engineering}, author={Gong, S. and Ma, W. and Dinh, T.-N.}, year={2012}, pages={486–494} }
 @inproceedings{dinh_nourgaliev_youngblood_2011, title={A system simulation code to support the safety case in the LVVR life extension: Selection, development, and testing of code architecture and solution algorithms, invited}, volume={104}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84875674404&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Dinh, T.-N. and Nourgaliev, R.R. and Youngblood, R.W.}, year={2011}, pages={951–953} }
 @article{gong_ma_dinh_2011, title={An experimental study of rupture dynamics of evaporating liquid films on different heater surfaces}, volume={54}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78751643541&partnerID=MN8TOARS}, DOI={10.1016/j.ijheatmasstransfer.2010.11.036}, abstractNote={Experimental data were obtained to reveal the complex dynamics of thin liquid films evaporating on heated horizontal surfaces, including formation and expansion of dry spots that occur after the liquid films decreased below critical thicknesses. The critical thickness of water film evaporating on various material surfaces is measured in the range of 60–150 μm, increasing with contact angle and heat flux while decreasing with thermal conductivity of the heater material. In the case of hexane evaporating on a titanium surface, the liquid film is found resilient to rupture, but starts oscillating as the averaged film thickness decreases below 15 μm.}, number={7-8}, journal={International Journal of Heat and Mass Transfer}, author={Gong, S. and Ma, W. and Dinh, T.-N.}, year={2011}, pages={1538–1547} }
 @inproceedings{youngblood_nourgaliev_kelly_smith_dinh_2011, title={Framework for applying a next-generation safety analysis code to plant life extension decision making, invited}, volume={104}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84875658203&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Youngblood, R.W. and Nourgaliev, R.R. and Kelly, D.L. and Smith, C.L. and Dinh, T.-N.}, year={2011}, pages={949–950} }
 @inproceedings{youngblood_nourgaliev_kelly_smith_dinh_2011, title={Heartbeat model for component failure time in simulation of plant behavior}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-80051988899&partnerID=MN8TOARS}, booktitle={International Topical Meeting on Probabilistic Safety Assessment and Analysis 2011, PSA 2011}, author={Youngblood, R.W. and Nourgaliev, R.R. and Kelly, D.L. and Smith, C.L. and Dinh, T.-N.}, year={2011}, pages={646–654} }
 @inproceedings{nourgaliev_dinh_nelson_2011, title={Lessons learned from an initial VU-assessed code development effort}, volume={104}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84875659394&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Nourgaliev, R.R. and Dinh, T.-N. and Nelson, R.A.}, year={2011}, pages={358–360} }
 @inproceedings{bui_nourgaliev_dinh_2011, title={On physics modeling and components development in R7}, volume={104}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84875679207&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Bui, A. and Nourgaliev, R.R. and Dinh, T.-N.}, year={2011}, pages={523–525} }
 @article{luo_luo_nourgaliev_mousseau_dinh_2010, title={A reconstructed discontinuous Galerkin method for the compressible Navier–Stokes equations on arbitrary grids}, volume={229}, ISSN={0021-9991}, url={http://dx.doi.org/10.1016/j.jcp.2010.05.033}, DOI={10.1016/j.jcp.2010.05.033}, abstractNote={A reconstruction-based discontinuous Galerkin (RDG) method is presented for the solution of the compressible Navier–Stokes equations on arbitrary grids. The RDG method, originally developed for the compressible Euler equations, is extended to discretize viscous and heat fluxes in the Navier–Stokes equations using a so-called inter-cell reconstruction, where a smooth solution is locally reconstructed using a least-squares method from the underlying discontinuous DG solution. Similar to the recovery-based DG (rDG) methods, this reconstructed DG method eliminates the introduction of ad hoc penalty or coupling terms commonly found in traditional DG methods. Unlike rDG methods, this RDG method does not need to judiciously choose a proper form of a recovered polynomial, thus is simple, flexible, and robust, and can be used on arbitrary grids. The developed RDG method is used to compute a variety of flow problems on arbitrary meshes to demonstrate its accuracy, efficiency, robustness, and versatility. The numerical results indicate that this RDG method is able to deliver the same accuracy as the well-known Bassi–Rebay II scheme, at a half of its computing costs for the discretization of the viscous fluxes in the Navier–Stokes equations, clearly demonstrating its superior performance over the existing DG methods for solving the compressible Navier–Stokes equations.}, number={19}, journal={Journal of Computational Physics}, publisher={Elsevier BV}, author={Luo, Hong and Luo, Luqing and Nourgaliev, Robert and Mousseau, Vincent A. and Dinh, Nam}, year={2010}, month={Sep}, pages={6961–6978} }
 @article{tran_kudinov_dinh_2010, title={An approach to numerical simulation and analysis of molten corium coolability in a boiling water reactor lower head}, volume={240}, ISSN={0029-5493}, url={http://dx.doi.org/10.1016/j.nucengdes.2009.11.029}, DOI={10.1016/j.nucengdes.2009.11.029}, abstractNote={This paper discusses an approach for application of the computational fluid dynamics (CFD) method to support development and validation of computationally effective methods for safety analysis, on the example of molten corium coolability in a BWR lower head. The approach consists of five steps designed to ensure physical soundness of the effective method simulation results: (i) analysis and decomposition of a severe accident problem into a set of separate-effect phenomena, (ii) validation of the CFD models on relevant separate-effect experiments for the reactor prototypical ranges of governing parameters, (iii) development of effective models and closures on the base of physical insights gained from relevant experiments and CFD simulations, (iv) using data from the integral experiments and CFD simulations performed under reactor prototypic conditions for validation of the effective model with quantification of uncertainty in the prediction results and (v) application of the computationally effective model to simulate and analyze the severe accident transient under consideration, including sensitivity and uncertainty analysis. Implementation of the approach is illustrated on a so-called effective convectivity model for simulation of turbulent natural convection heat transfer and phase changes in a decay-heated corium pool. It is shown that detailed information obtained from the CFD simulations are instrumental to ensure the effective models capture safety-significant local phenomena, e.g. the enhanced downward heat flux in the vicinity of a cooled control rod guide tube.}, number={9}, journal={Nuclear Engineering and Design}, publisher={Elsevier BV}, author={Tran, C.T. and Kudinov, P. and Dinh, T.N.}, year={2010}, month={Sep}, pages={2148–2159} }
 @article{gong_ma_dinh_2010, title={Diagnostic techniques for the dynamics of a thin liquid film under forced flow and evaporating conditions}, volume={9}, ISSN={1613-4982 1613-4990}, url={http://dx.doi.org/10.1007/S10404-010-0626-Z}, DOI={10.1007/s10404-010-0626-z}, number={6}, journal={Microfluidics and Nanofluidics}, publisher={Springer Science and Business Media LLC}, author={Gong, Shengjie and Ma, Weimin and Dinh, Truc-Nam}, year={2010}, month={May}, pages={1077–1089} }
 @article{kudinov_karbojian_weimin_dinh_2010, title={The defor-s experimental study of debris formation with corium simulant materials}, volume={170}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77951003760&partnerID=MN8TOARS}, DOI={10.13182/NT10-A9460}, abstractNote={Characteristics of corium debris beds formed in a severe core melt accident are studied in the Debris Bed Formation-Snapshot (DEFOR-S) test campaign, in which superheated binary-oxidic melts (both eutectic and noneutectic compositions) as the corium simulants are discharged into a water pool. Water subcooling and pool depth are found to significantly influence the debris fragments’ morphology and agglomeration. When particle agglomeration is absent, the tests produced debris beds with porosity of ~60 to 70%. This porosity is significantly higher than the ~40% porosity broadly used in contemporary analysis of corium debris coolability in light water reactor severe accidents. The impact of debris formation on corium coolability is further complicated by debris fragments’ sharp edges, roughened surfaces, and cavities that are partially or fully encapsulated within the debris fragments. These observations are made consistently in both the DEFOR-S experiments and other tests with prototypic and simulant corium melts. Synthesis of the debris fragments from the DEFOR-S tests conducted under different melt and coolant conditions reveal trends in particle size, particle sphericity, surface roughness, sharp edges, and internal porosity as functions of water subcooling and melt composition. Qualitative analysis and discussion reaffirm the complex interplay between contributing processes (droplet interfacial instability and breakup, droplet cooling and solidification, cavity formation and solid fracture) on particle morphology and, consequently, on the characteristics of the debris beds.}, number={1}, journal={Nuclear Technology}, author={Kudinov, P. and Karbojian, A. and Weimin, Ma. and Dinh, T.-N.}, year={2010}, pages={219–230} }
 @article{ma_dinh_2010, title={The effects of debris bed's prototypical characteristics on corium coolability in a LWR severe accident}, volume={240}, ISSN={0029-5493}, url={http://dx.doi.org/10.1016/j.nucengdes.2009.10.026}, DOI={10.1016/j.nucengdes.2009.10.026}, abstractNote={This paper is concerned with coolability assessment of a debris bed formed in fuel coolant interactions (FCIs) during a hypothetical severe accident in a light water reactor (LWR). The focus is placed the potential effect of the bed's prototypical characteristics on its coolability, in terms of (i) porosity range, (ii) multi-dimensionality, (iii) inhomogeneity, (iv) particle morphology, and (v) heat generation method (e.g. volumetric heating vs. local heaters). The analysis results indicate availability of substantial coolability margins compared to previous assessments based on models and experiments using an idealized bed configuration (e.g. 1D homogenous debris layer). Notably, high porosity (up to 70%) of debris beds, obtained in experiments and expected to be the case of prototypical debris beds, could increase the dryout heat flux by 100% and more, depending on particle size, compared with the dryout heat flux predicted for debris beds with traditionally assumed porosity of approximately 40%. Bed inhomogeneity represented by micro-channels in a mini bed is predicted to enhance the dryout heat flux by up to ∼50%, even if the micro-channels occupy only a small volume fraction (e.g., less than 4%) of the bed. The effect of coolant side ingress into a multidimensional bed is predicted to enhance the dryout heat flux by up to 40% for the beds analyzed.}, number={3}, journal={Nuclear Engineering and Design}, publisher={Elsevier BV}, author={Ma, Weimin and Dinh, Truc-Nam}, year={2010}, month={Mar}, pages={598–608} }
 @article{karbojian_ma_kudinov_dinh_2009, title={A scoping study of debris bed formation in the DEFOR test facility}, volume={239}, ISSN={0029-5493}, url={http://dx.doi.org/10.1016/j.nucengdes.2009.03.002}, DOI={10.1016/j.nucengdes.2009.03.002}, abstractNote={Motivated to understand the processes which govern the formation and characteristics of a debris bed and hence its coolability during a postulated severe accident of a light water reactor, a new research program called DEFOR (DEbris FORmation) was initiated at the Royal Institute of Technology (KTH). This paper presents results obtained in scoping experiments conducted during an initial phase of the DEFOR program. The DEFOR-E test campaign is concerned with the DEFOR test facility commissioning and exploratory study of phenomena occurred during a debris bed formation. Binary oxide mixtures at different superheat temperatures were used as the corium melt simulants. The scoping experiments revealed the effect of water pool depth and subcooling, melt mass and material properties on the debris bed characteristics. Insights gained from the DEFOR-E test campaign help guide the scaling, design and operation of the subsequent experiments in the DEFOR program.}, number={9}, journal={Nuclear Engineering and Design}, publisher={Elsevier BV}, author={Karbojian, A. and Ma, W.M. and Kudinov, P. and Dinh, T.N.}, year={2009}, month={Sep}, pages={1653–1659} }
 @article{hansson_park_dinh_2009, title={Dynamics and preconditioning in a single-droplet vapor explosion}, volume={167}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-68649118880&partnerID=MN8TOARS}, DOI={10.13182/NT09-A8864}, abstractNote={Abstract The present study aims to develop a mechanistic understanding of the thermal-hydraulic processes in a vapor explosion, which may occur in nuclear power plants during a hypothetical severe accident, involving interactions of high-temperature corium melt and volatile coolant. Dynamics of the hot liquid (melt) droplet and the volatile liquid (coolant) were investigated in the Micro-Interactions in Steam Explosion Experiments (MISTEE) facility by performing well-controlled, externally triggered, single-droplet experiments, using a high-speed visualization system with synchronized digital cinematography and continuous X-ray radiography, called Simultaneous High-speed Acquisition of X-ray Radiography and Photography (SHARP). After an elaborate image processing, the SHARP images depict the evolution of both melt material (dispersal) and coolant (bubble dynamics) and their microscale interactions. The analysis of the data shows a deficiency in using the bubble dynamics alone to provide a consistent explanation of the energetic behavior. In contrast, the SHARP data reveal a correlation between the droplet’s dynamics in the bubble’s first cycle and the energetics of the subsequent explosive evaporation in the bubble’s second cycle. The finding provides a basis to suggest that a so-called melt-droplet preconditioning, i.e., deformation/prefragmentation of a hot melt droplet immediately following the pressure trigger, is instrumental to the subsequent coolant entrainment, evaporation, and energetics of the resulting vapor explosion.}, number={1}, journal={Nuclear Technology}, author={Hansson, R.C. and Park, H.S. and Dinh, T.-N.}, year={2009}, pages={223–234} }
 @inproceedings{hess_dinh_gaertner_szilard_2009, title={Risk-informed safety margin characterization}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77952875137&partnerID=MN8TOARS}, DOI={10.1115/ICONE17-75064}, abstractNote={The concept of safety margins has served as a fundamental principle in the design and operation of commercial nuclear power plants (NPPs). Defined as the minimum distance between a system’s “loading” and its “capacity”, plant design and operation is predicated on ensuring an adequate safety margin for safety-significant parameters (e.g., fuel cladding temperature, containment pressure, etc.) is provided over the spectrum of anticipated plant operating, transient and accident conditions. To meet the anticipated challenges associated with extending the operational lifetimes of the current fleet of operating NPPs, the United States Department of Energy (USDOE), the Idaho National Laboratory (INL) and the Electric Power Research Institute (EPRI) have developed a collaboration to conduct coordinated research to identify and address the technological challenges and opportunities that likely would affect the safe and economic operation of the existing NPP fleet over the postulated long-term time horizons. In this paper we describe a framework for developing and implementing a Risk-Informed Safety Margin Characterization (RISMC) approach to evaluate and manage changes in plant safety margins over long time horizons.}, booktitle={International Conference on Nuclear Engineering, Proceedings, ICONE}, author={Hess, S.M. and Dinh, N. and Gaertner, J.P. and Szilard, R.}, year={2009}, pages={11–17} }
 @article{tran_dinh_2009, title={Simulation of core melt pool formation in a Reactor pressure vessel lower head using an Effective Convectivity Model}, volume={41}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70350161939&partnerID=MN8TOARS}, DOI={10.5516/NET.2009.41.7.929}, abstractNote={The present study is concerned with the extension of the Effective Convectivity Model (ECM) to the phase-change problem to simulate the dynamics of the melt pool formation in a Light Water Reactor (LWR) lower plenum during hypothetical severe accident progression. The ECM uses heat transfer characteristic velocities to describe turbulent natural convection of a melt pool. The simple approach of the ECM method allows implementing different models of the characteristic velocity in a mushy zone for non-eutectic mixtures. The Phase-change ECM (PECM) was examined using three models of the characteristic velocities in a mushy zone and its performance was compared. The PECM was validated using a dual-tier approach, namely validations against existing experimental data (the SIMECO experiment) and validations against results obtained from Computational Fluid Dynamics (CFD) simulations. The results predicted by the PECM implementing the linear dependency of mushy-zone characteristic velocity on fluid fraction are well agreed with the experimental correlation and CFD simulation results. The PECM was applied to simulation of melt pool formation heat transfer in a Pressurized Water Reactor (PWR) and Boiling Water Reactor (BWR) lower plenum. The study suggests that the PECM is an adequate and effective tool to compute the dynamics of core melt pool formation.}, number={7}, journal={Nuclear Engineering and Technology}, author={Tran, C.-T. and Dinh, T.-N.}, year={2009}, pages={929–944} }
 @article{hansson_park_dinh_2009, title={Simultaneous high speed digital cinematographic and X-ray radiographic imaging of a intense multi-fluid interaction with rapid phase changes}, volume={33}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-72549099529&partnerID=MN8TOARS}, DOI={10.1016/j.expthermflusci.2009.01.011}, abstractNote={As typical for the study of the vapor explosions, the qualitative and quantitative understanding of the phenomena requires visualization of both material and interface dynamics. A new approach to multi-fluid multiphase visualization is presented with the focus on the development of a synchronized high-speed visualization by digital cinematography and X-ray radiography. The developed system, named SHARP (simultaneous high-speed acquisition of X-ray radiography and photography), and its image processing methodology, directed to an image synchronization procedure and a separate quantification of vapor and molten material dynamics, is presented in this paper. Furthermore, we exploit an intrinsic property of the X-ray radiation, namely the differences in linear mass attenuation coefficients over the beam path through a multi-component system, to characterize the evolution of molten material distribution. Analysis of the data obtained by the SHARP system and image processing procedure developed granted new insights into the physics of the vapor explosion phenomena, as well as, quantitative information of the associated dynamic micro-interactions.}, number={4}, journal={Experimental Thermal and Fluid Science}, author={Hansson, R.C. and Park, H.S. and Dinh, T.-N.}, year={2009}, pages={754–763} }
 @article{tran_dinh_2009, title={The effective convectivity model for simulation of melt pool heat transfer in a light water reactor pressure vessel lower head. Part I: Physical processes, modeling and model implementation}, volume={51}, ISSN={0149-1970}, url={http://dx.doi.org/10.1016/j.pnucene.2009.06.007}, DOI={10.1016/j.pnucene.2009.06.007}, abstractNote={This paper, and its companion paper [Tran C.T., Dinh, T.N. The effective convectivity model for simulation of melt pool heat transfer in a light water reactor pressure vessel lower head. Part II: Model assessment and application. Progress in Nuclear Energy (companion paper), in preparation] document the development, validation and applications of a simulation platform for computationally-effective, sufficiently-accurate numerical predictions of core melt-structure-water interactions in the light water reactor lower head during a postulated severe core-melting accident. The centerpiece of this work is the Effective Convectivity Model (ECM) for description of energy splitting in a core melt pool. Built on the concept of characteristic velocities in Effective Convectivity Conductivity Model and supported by the key findings obtained from Computational Fluid Dynamics (CFD) simulations of turbulent natural convection, heat transfer and phase changes in volumetrically heated liquid pools, the ECM is refined and extended to three-dimensions and phase changes to enable simulations of melt pool formation and corium coolability in complex geometry such as a Boiling Water Reactor (BWR) lower plenum.}, number={8}, journal={Progress in Nuclear Energy}, publisher={Elsevier BV}, author={Tran, Chi-Thanh and Dinh, Truc-Nam}, year={2009}, month={Nov}, pages={849–859} }
 @article{tran_dinh_2009, title={The effective convectivity model for simulation of melt pool heat transfer in a light water reactor pressure vessel lower head. Part II: Model assessment and application}, volume={51}, ISSN={0149-1970}, url={http://dx.doi.org/10.1016/j.pnucene.2009.06.001}, DOI={10.1016/j.pnucene.2009.06.001}, abstractNote={The paper reports detailed assessments and representative application of the effective convectivity model (ECM) developed and described in the companion paper (Tran and Dinh, submitted for publication). The ECM capability to accurately predict energy splitting and heat flux profiles in volumetrically heated liquid pools of different geometries over a range of conditions related to accident progression is examined and benchmarked against both experimental data and CFD results. Augmented with models for phase changes in binary mixture, the resulting PECM (phase-change ECM) is validated against a non-eutectic heat transfer experiment. The PECM tool is then applied to predict thermal loads imposed on the reactor vessel wall and Control Rod Guide Tubes (CRGTs) during core debris heatup and melting in the BWR lower plenum. The reactor-scale simulations demonstrate the PECM's high computational performance, particularly needed to analyze processes during long transients of severe accidents. The analysis provides additional arguments to support an outstanding potential of using the CRGT cooling as a severe accident management measure to delay the vessel failure and increase the likelihood of in-vessel core melt retention in the BWR.}, number={8}, journal={Progress in Nuclear Energy}, publisher={Elsevier BV}, author={Tran, Chi-Thanh and Dinh, Truc-Nam}, year={2009}, month={Nov}, pages={860–871} }
 @article{ma_karbojian_sehgal_dinh_2009, title={Thermal-hydraulic performance of heavy liquid metal in straight-tube and U-tube heat exchangers}, volume={239}, ISSN={0029-5493}, url={http://dx.doi.org/10.1016/j.nucengdes.2009.03.014}, DOI={10.1016/j.nucengdes.2009.03.014}, abstractNote={Motivated by an increased interest in heavy liquid metal (lead or lead alloy) cooled fast reactors (LFR) and accelerator-driven system (ADS), the present paper presents a study on resistance characteristics and heat transfer performance of liquid lead bismuth eutectic (LBE) flow through a straight-tube heat exchanger and a U-tube heat exchanger. The investigation is performed on the TALL test facility at KTH. The heat exchangers have counter-current flow arrangement, and are made from a pair of 1-m-long concentric ducts, with the LBE flowing in the inner tube of 10 mm I.D. and the secondary coolant flowing in the annulus. The inlet temperature of LBE into the heat exchangers is from 200 °C to 450 °C with temperature drops from 0 °C to 100 °C within the LBE flow range of Re = 104–105. Analysis of the experimental results obtained provides a basic understanding and quantification of the regimes of lead–bismuth flow and heat transfer through a straight tube and a U-shaped tube. The unique data base also serves as benchmark and improvement for system thermal-hydraulic codes (e.g. RELAP, TRAC/AAA) whose development and testing were dominantly driven by applications in water-cooled systems. Lessons and insights learnt from the study and recommendations for the heat exchanger selection are discussed.}, number={7}, journal={Nuclear Engineering and Design}, publisher={Elsevier BV}, author={Ma, Weimin and Karbojian, Aram and Sehgal, Bal Raj and Dinh, Truc-Nam}, year={2009}, month={Jul}, pages={1323–1330} }
 @inproceedings{kudinov_dinh_2008, title={A computational study of debris bed formation}, volume={98}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-55249101472&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Kudinov, P. and Dinh, T.N.}, year={2008}, pages={341–342} }
 @inproceedings{kudinov_karbojian_ma_davydov_dinh_2008, title={A study of ex-vessel debris formation in a LWR severe accident}, volume={5}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-52249116051&partnerID=MN8TOARS}, booktitle={Societe Francaise d'Energie Nucleaire - International Congress on Advances in Nuclear Power Plants - ICAPP 2007, "The Nuclear Renaissance at Work"}, author={Kudinov, P. and Karbojian, A. and Ma, W. and Davydov, M. and Dinh, T.-N.}, year={2008}, pages={2848–2859} }
 @inproceedings{roshan_ma_kozlowski_dinh_2008, title={A study of reactor systems during a loss of offsite electric power in Forsmark-1 plant}, volume={4}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-52249089150&partnerID=MN8TOARS}, booktitle={Societe Francaise d'Energie Nucleaire - International Congress on Advances in Nuclear Power Plants - ICAPP 2007, "The Nuclear Renaissance at Work"}, author={Roshan, S.S. and Ma, W. and Kozlowski, T. and Dinh, T.-N.}, year={2008}, pages={2642–2651} }
 @inproceedings{tran_dinh_2008, title={An effective convectivity model for simulation of in-vessel core melt progression in a boiling water reactor}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-52249091307&partnerID=MN8TOARS}, booktitle={Societe Francaise d'Energie Nucleaire - International Congress on Advances in Nuclear Power Plants - ICAPP 2007, "The Nuclear Renaissance at Work"}, author={Tran, C.-T. and Dinh, T.-N.}, year={2008}, pages={925–935} }
 @inproceedings{kudinov_karbojian_ma_dinh_2008, title={An experimental study on debris formation with corium simulant materials}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70349971077&partnerID=MN8TOARS}, booktitle={International Conference on Advances in Nuclear Power Plants, ICAPP 2008}, author={Kudinov, P. and Karbojian, A. and Ma, W. and Dinh, T.-N.}, year={2008}, pages={1191–1199} }
 @inproceedings{tran_dinh_2008, title={Application of the phase-change effective convectivity model to analysis of core melt pool formation and heat transfer in a BWR lower head}, volume={98}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-55249125206&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Tran, C.T. and Dinh, T.N.}, year={2008}, pages={617–618} }
 @inproceedings{kubarev_kozlowski_roshan_dinh_2008, title={Design of BWR instability suppression system}, volume={3}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79953854518&partnerID=MN8TOARS}, booktitle={International Conference on the Physics of Reactors 2008, PHYSOR 08}, author={Kubarev, A. and Kozlowski, T. and Roshan, S.S. and Dinh, T.-N.}, year={2008}, pages={2062–2068} }
 @inproceedings{hansson_dinh_2008, title={Effect of non-condensable gases on triggering and energetics of a single drop vapor explosion}, volume={98}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-55249084649&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Hansson, R.C. and Dinh, T.-N.}, year={2008}, pages={547–548} }
 @inproceedings{journeau_bonnet_godin-jacqmin_piluso_tarabelli_dufour_spindler_nicolas_altstadt_atkhen_et al._2008, title={European Research on the Corium issues within the SARNET network of excellence}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70349974746&partnerID=MN8TOARS}, booktitle={International Conference on Advances in Nuclear Power Plants, ICAPP 2008}, author={Journeau, C. and Bonnet, J.M. and Godin-Jacqmin, L. and Piluso, P. and Tarabelli, D. and Dufour, E. and Spindler, B. and Nicolas, L. and Altstadt, E. and Atkhen, K. and et al.}, year={2008}, pages={1172–1181} }
 @article{theofanous_dinh_2008, title={Integration of multiphase science and technology with risk management in nuclear power reactors}, volume={20}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-56749153492&partnerID=MN8TOARS}, DOI={10.1615/MultScienTechn.v20.i2.10}, abstractNote={Application of the Risk-Oriented Accident Analysis Methodology to the Economic, Simplified Boiling Water Reactor Design.}, number={2}, journal={Multiphase Science and Technology}, author={Theofanous, T.G. and Dinh, T.-N.}, year={2008}, pages={81–211} }
 @inproceedings{yakush_kudinov_dinh_2008, title={Modeling of two-phase natural convection flows in a water pool with a decay-heated debris bed}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70349970186&partnerID=MN8TOARS}, booktitle={International Conference on Advances in Nuclear Power Plants, ICAPP 2008}, author={Yakush, S. and Kudinov, P. and Dinh, T.-N.}, year={2008}, pages={1141–1150} }
 @inproceedings{dinh_2008, title={Multiphase flow phenomena of steam generator tube rupture in a lead-cooled reactor system: A scoping analysis}, volume={5}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-52249098812&partnerID=MN8TOARS}, booktitle={Societe Francaise d'Energie Nucleaire - International Congress on Advances in Nuclear Power Plants - ICAPP 2007, "The Nuclear Renaissance at Work"}, author={Dinh, T.-N.}, year={2008}, pages={2765–2775} }
 @inproceedings{dinh_hansson_kudinov_2008, title={On solidification mechanism that governs the effect of binary melt composition on steam explosion energetics}, volume={98}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-55249084402&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Dinh, T.-N. and Hansson, R.C. and Kudinov, P.}, year={2008}, pages={615–616} }
 @inproceedings{cadinu_kozlowski_dinh_2008, title={Relating system-to-CFD coupled code analyses to theoretical framework of a multiscale method}, volume={5}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-52249115142&partnerID=MN8TOARS}, booktitle={Societe Francaise d'Energie Nucleaire - International Congress on Advances in Nuclear Power Plants - ICAPP 2007, "The Nuclear Renaissance at Work"}, author={Cadinu, F. and Kozlowski, T. and Dinh, T.-N.}, year={2008}, pages={2959–2967} }
 @inproceedings{kozlowski_peltonen_dinh_2008, title={Spatial coupling for BWR stability analysis}, volume={98}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-55249127520&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Kozlowski, T. and Peltonen, J. and Dinh, T.-N.}, year={2008}, pages={603–605} }
 @inproceedings{peltonen_kozlowski_dinh_2008, title={Spatial coupling for coupled code safety analysis of BWR design-basis accidents}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79953889385&partnerID=MN8TOARS}, booktitle={International Conference on the Physics of Reactors 2008, PHYSOR 08}, author={Peltonen, J. and Kozlowski, T. and Dinh, T.-N.}, year={2008}, pages={1313–1320} }
 @article{dombrovsky_dinh_2008, title={The effect of thermal radiation on the solidification dynamics of metal oxide melt droplets}, volume={238}, ISSN={0029-5493}, url={http://dx.doi.org/10.1016/j.nucengdes.2007.10.010}, DOI={10.1016/j.nucengdes.2007.10.010}, abstractNote={Cooling and solidification of metal oxide droplets in water are considered, using a single-particle model which takes into account heat conduction and thermal radiation transfer within the particle. It is shown that, for millimeter-size particles, near-infrared absorption of the particle's substance determines the solidification pattern and dynamics. For semi-transparent aluminum oxide particles, the rate of surface solidification is controlled by convective heat transfer. For opaque corium particles, thermal radiation from the particle surface leads to fast surface solidification. The impact of so-formed crust layer on subsequent particle fragmentation is discussed with respect to its influence on steam explosion.}, number={6}, journal={Nuclear Engineering and Design}, publisher={Elsevier BV}, author={Dombrovsky, Leonid A. and Dinh, Truc-Nam}, year={2008}, month={Jun}, pages={1421–1429} }
 @inproceedings{weimin_dinh_2007, title={A study on effects of debris bed prototypicality on coolability}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-44349091618&partnerID=MN8TOARS}, booktitle={Proceedings - 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-12}, author={Weimin, M. and Dinh, T.-N.}, year={2007} }
 @article{theofanous_li_dinh_chang_2007, title={Aerobreakup in disturbed subsonic and supersonic flow fields}, volume={593}, ISSN={0022-1120 1469-7645}, url={http://dx.doi.org/10.1017/S0022112007008853}, DOI={10.1017/S0022112007008853}, abstractNote={This work concerns the breakup of millimetre-scale liquid droplets in gaseous flow fields that are disturbed from free-stream conditions by the presence of solid obstacles or other drops. A broad range of flow conditions is considered – from subsonic to supersonic, from highly rarefied to ambient pressures, and from fixed cylindrical obstacles to free liquid droplets (as obstacles). The liquid is water or tributyl phosphate, a water-like low-viscosity fluid of very low vapour pressure. We present data on deformation and breakup regimes, and, aided by numerical simulations, we discuss governing mechanisms and the time scaling of these events. Thereby a methodology is demonstrated for conveniently forecasting first-order behaviours in disturbed flow fields more generally. The highly resolved images lend themselves to testing/benchmarking numerical simulations of interfacial flows. These results, along with the experimental capability developed, constitute one of the key building blocks for our overall long-term aim towards predicting ultimate particle-size distributions from such intense aerodynamic interactions involving very large quantities of Newtonian and viscoelastic liquids.}, journal={Journal of Fluid Mechanics}, publisher={Cambridge University Press (CUP)}, author={Theofanous, T. G. and Li, G. J. and Dinh, T. N. and Chang, C. H.}, year={2007}, month={Nov}, pages={131–170} }
 @inproceedings{kudinov_dinh_2007, title={An analytical study of mechanisms that govern debris packing in a LWR severe accident}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-44349098203&partnerID=MN8TOARS}, booktitle={Proceedings - 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-12}, author={Kudinov, P. and Dinh, N.}, year={2007} }
 @inproceedings{hansson_park_dinh_2007, title={Dynamics and preconditioning in a single drop vapor explosion}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-44349165747&partnerID=MN8TOARS}, booktitle={Proceedings - 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-12}, author={Hansson, R.C. and Park, H.S. and Dinh, T.N.}, year={2007} }
 @inproceedings{kozlowski_roshan_dinh_2007, title={Evaluation of coupled codes RELAP5/PARCS capability for BWR global stability prediction}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-44349116232&partnerID=MN8TOARS}, booktitle={Proceedings - 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-12}, author={Kozlowski, T. and Roshan, S. and Dinh, T.-N.}, year={2007} }
 @inproceedings{dinh_2007, title={Material property effect in steam explosion energetics: Revisited}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-42249093642&partnerID=MN8TOARS}, booktitle={Proceedings - 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-12}, author={Dinh, T.-N.}, year={2007} }
 @inproceedings{suchoszek_cadinu_kozlowski_dinh_2007, title={RELAP5 and TRACE codes comparison and validation under steady-state and transient conditions on the basis of NUPEC data}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-44349127315&partnerID=MN8TOARS}, booktitle={Proceedings - 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-12}, author={Suchoszek, J. and Cadinu, F. and Kozlowski, T. and Dinh, T.-N.}, year={2007} }
 @inproceedings{tran_dinh_2007, title={Simulation of core melt pool formation in a reactor pressure vessel lower head using an effective convectivity model}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-44449162101&partnerID=MN8TOARS}, booktitle={Proceedings - 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-12}, author={Tran, C.-T. and Dinh, T.-N.}, year={2007} }
 @inproceedings{weimin_karbojian_sehgal_dinh_2007, title={Thermal-hydraulic performance of lead-bismuth eutectic in a straight-tube and a U-tube heat exchangers}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-44349134568&partnerID=MN8TOARS}, booktitle={Proceedings - 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-12}, author={Weimin, M. and Karbojian, A. and Sehgal, B.R. and Dinh, T.-N.}, year={2007} }
 @book{nourgaliev_dinh_theofanous_2006, title={Adaptive characteristics-based matching (aCBM): A method for interfacial dynamics in compressible multiphase flows}, volume={81}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84859928528&partnerID=MN8TOARS}, DOI={10.1007/1-4020-4977-3_34}, journal={Fluid Mechanics and its Applications}, author={Nourgaliev, R. and Dinh, N. and Theofanous, T.}, year={2006}, pages={341–352} }
 @article{nourgaliev_dinh_theofanous_2006, title={Adaptive characteristics-based matching for compressible multifluid dynamics}, volume={213}, ISSN={0021-9991}, url={http://dx.doi.org/10.1016/j.jcp.2005.08.028}, DOI={10.1016/j.jcp.2005.08.028}, abstractNote={This paper presents an evolutionary step in sharp capturing of shocked, high acoustic impedance mismatch (AIM) interfaces in an adaptive mesh refinement (AMR) environment. The central theme which guides the present development addresses the need to optimize between the algorithmic complexities in advanced front capturing and front tracking methods developed recently for high AIM interfaces with the simplicity requirements imposed by the AMR multi-level dynamic solutions implementation. The paper shows that we have achieved this objective by means of relaxing the strict conservative treatment of AMR prolongation/restriction operators in the interfacial region and by using a natural-neighbor-interpolation (NNI) algorithm to eliminate the need for ghost cell extrapolation into the other fluid in a characteristics-based matching (CBM) scheme. The later is based on a two-fluid Riemann solver, which brings the accuracy and robustness of front-tracking approach into the fast local level set front-capturing implementation of the CBM method. A broad set of test problems (including shocked multi-gaseous media, bubble collapse, underwater explosion and shock passing over a liquid drop suspended in a gaseous medium) was performed and the results demonstrate that the fundamental assumptions/approximations made in modifying the AMR prolongation/restriction operators and in using the NNI algorithm for interfacial treatment are acceptable from the accuracy point of view, while they enable an effective implementation and utility of the structured AMR technology for solving complex multiphase problems in a highly compressible setting.}, number={2}, journal={Journal of Computational Physics}, publisher={Elsevier BV}, author={Nourgaliev, R.R. and Dinh, T.N. and Theofanous, T.G.}, year={2006}, month={Apr}, pages={500–529} }
 @inproceedings{tran_dinh_2006, title={Analysis of melt pool heat transfer in a BWR lower head}, volume={95}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33845527584&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Tran, C.T. and Dinh, T.N.}, year={2006}, pages={629–631} }
 @book{theofanous_nourgaliev_li_dinh_2006, title={Compressible multi-hydrodynamics (CMH): Breakup, mixing and dispersal of liquids/solids in high speed flows}, volume={81}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84859933947&partnerID=MN8TOARS}, DOI={10.1007/1-4020-4977-3_35}, journal={Fluid Mechanics and its Applications}, author={Theofanous, T. and Nourgaliev, R. and Li, G. and Dinh, N.}, year={2006}, pages={353–369} }
 @article{theofanous_dinh_2006, title={High heat flux boiling and burnout as microphysical phenomena: Mounting evidence and opportunities}, volume={18}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33749023903&partnerID=MN8TOARS}, DOI={10.1615/MultScienTechn.v18.i3.30}, abstractNote={In our recent works Theofanous et al., 2002a-b, we have demonstrated that burnout in pool boiling is not hydrodynamically limited, at least not in the sense that has been perceived in the past. In this paper, we discuss the opportunities created by the new understanding of mechanisms that govern the boiling crisis. This understanding is built upon a scales separation phenomenon, referring to a vapor blanket separating the liquid film on the heater surface from the chaotic, churning flow in the two-phase pool. In essence, the scales separation suggests that mechanisms of boiling crisis should be sought within the micro-hydrodynamics of the evaporating liquid microlayer rather than in the pool thermal-hydraulics. Detail analysis of surface temperature patterns obtained by infrared imaging at high heat fluxes points to a nearly static picture of boiling heat transfer, with intense cooling at locations which were nucleation sites activated at lower heat fluxes. Furthermore, we show that control of the surface and coolant chemistry offers the potential to enhance resistance to burnout and achieve critical heat fluxes (CHF) exceeding those defined by the so-called hydrodynamic limit. Our more recent experiments show an improved resilience of the heater to burnout when a high-solubility salt or nanoparticles are added to the coolant (water). We explain the observed phenomenon through the increase in disjoining pressure at the meniscus contact line that promotes liquid spreading towards the dry area. It is noteworthy that the scales separation phenomenon provides a basis to suggest that mechanisms of enhancement to burnout in pool boiling are also active, even to a larger extent, in spray cooling and flow boiling.}, number={3}, journal={Multiphase Science and Technology}, author={Theofanous, T.G. and Dinh, T.N.}, year={2006}, pages={251–276} }
 @article{dinh_bürger_lohnert_2006, title={Introduction to the Festschrift honoring the 70th Birthday of Professor Bal Raj Sehgal}, volume={236}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33746739500&partnerID=MN8TOARS}, DOI={10.1016/j.nucengdes.2006.04.029}, number={19-21}, journal={Nuclear Engineering and Design}, author={Dinh, N. and Bürger, M. and Lohnert, G.}, year={2006}, pages={1939–1940} }
 @article{dinh_nourgaliev_theofanous_2006, title={On the numerical simulation of acceleration-driven multi-fluid mixing}, volume={18}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33748998486&partnerID=MN8TOARS}, DOI={10.1615/MultScienTechn.v18.i3.10}, abstractNote={This paper is concerned with computational prediction of acceleration-induced multi-fluid mixing phenomena. Premises and performance of existing approaches are reviewed and analyzed with focus on a late phase behavior. We introduce a new framework whose central idea is to use an interfacial area transport equation (IATE) and a subgrid scale model (SGS) of multi-fluid turbulence to provide a natural transition from DNS-based simulation toward an effective-field model (EFM) and deeply into well-mixed states with continuous refinement of length scale. We present new results and important insights derived from our work on four platform technologies: DNS, EFM, IATE and SGS. We discuss the approach to ensure that developments in different areas effectively emerge and function seamlessly in an overall computational platform for multi-fluid mixing.}, number={3}, journal={Multiphase Science and Technology}, author={Dinh, T.N. and Nourgaliev, R.R. and Theofanous, T.G.}, year={2006}, pages={199–230} }
 @inproceedings{cadinu_kozlowski_dinh_2006, title={RELAP5 performance in predicting critical power in a BWR fuel bundle}, volume={95}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33845532848&partnerID=MN8TOARS}, booktitle={Transactions of the American Nuclear Society}, author={Cadinu, F. and Kozlowski, T. and Dinh, T.-N.}, year={2006}, pages={650–651} }
 @book{nourgaliev_dinh_nguyen_theofanous_2006, title={Treatment of particle collisions in direct numerical simulations of high speed compressible flows}, volume={81}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84859934549&partnerID=MN8TOARS}, journal={Fluid Mechanics and its Applications}, author={Nourgaliev, R. and Dinh, N. and Nguyen, L. and Theofanous, T.}, year={2006}, pages={247–259} }
 @inproceedings{nourgaliev_wiri_dinh_theofanous_2005, title={Adaptive strategies for mass conservation in level set treatment}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84884964371&partnerID=MN8TOARS}, booktitle={17th AIAA Computational Fluid Dynamics Conference}, author={Nourgaliev, R.R. and Wiri, S. and Dinh, T.N. and Theofanous, T.G.}, year={2005} }
 @inproceedings{li_dinh_yang_theofanous_2005, title={Investigation of breakup of isolated and multiple drops in subsonic flow}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-30744460145&partnerID=MN8TOARS}, booktitle={43rd AIAA Aerospace Sciences Meeting and Exhibit - Meeting Papers}, author={Li, G.J. and Dinh, T.N. and Yang, Y.Z. and Theofanous, T.G.}, year={2005}, pages={4995–5005} }
 @inproceedings{nourgaliev_suschikh_dinh_theofanous_2005, title={Numerical investigation of shock wave refraction patterns at multimaterial interfaces}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-30744447245&partnerID=MN8TOARS}, booktitle={43rd AIAA Aerospace Sciences Meeting and Exhibit - Meeting Papers}, author={Nourgaliev, R.R. and Suschikh, S.Y. and Dinh, T.N. and Theofanous, T.G.}, year={2005}, pages={10905–10921} }
 @article{nourgaliev_wiri_dinh_theofanous_2005, title={On improving mass conservation of level set by reducing spatial discretization errors}, volume={31}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-24044536557&partnerID=MN8TOARS}, DOI={10.1016/j.ijmultiphaseflow.2005.08.003}, abstractNote={The pore-scale mechanism of the waterflooding contributes to enhancing oil recovery, which has been widely emphasized in the petroleum industry. In this paper, the performances and accuracy of three tracking interface algorithms, including VOF, LS, and VOSET, are compared and analyzed through two-phase flow in the conceptual model of pore-throat. The results show that the VOSET method combines the advantages of the other two methods, which not only satisfies the mass conservation but also improves the continuity of the physical quantities near the interface. Then, based on the binary image of the pore, the two-dimensional micro pore model is reconstructed by extracting image contour. The grid independence of the reconstructed pore model is verified by the single-phase flow simulation. The waterflooding process in the reconstructed pore model is simulated using the VOSET method, and the effects of displacement speed and wettability on the oil recovery are analyzed. The morphologies of residual oil under different conditions of wettability are investigated and analyzed. The study provides a basic theory for modeling the pore-scale oil-water flow and optimizing the scheme of the water injection.}, number={12}, journal={International Journal of Multiphase Flow}, author={Nourgaliev, R.R. and Wiri, S. and Dinh, N.T. and Theofanous, T.G.}, year={2005}, pages={1329–1336} }
 @inproceedings{nourgaliev_dinh_theofanous_2005, title={Sharp treatment of surface tension and viscous stresses in multifluid dynamics}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85087598929&partnerID=MN8TOARS}, DOI={10.2514/6.2005-5349}, abstractNote={A new treatment for interfacial boundary conditions in viscous multifluid flows with surface tension is developed and tested. In difference to the �-formulation- and Continuum-Surface-Force-(CSF)-based methods, no smearing of material properties (viscosity, density, and surface tension force) is used. Instead, the interfacial jump conditions are introduced directly into the flux terms, using sharp resolution of the interface with subcell markers, within the framework of the level-set-based adaptive CharacteristicsBased Matching (aCBM) method, incorporated into the Structured Adaptive Mesh Refinement (SAMR) algorithm. This treatment exhibits significantly lower (up to three orders of magnitude) spurious velocities at the interface compared to the smearing approach, and is able to maintain sharp (within one node) jumps in pressure and viscous stresses. Performance is demonstrated on a series of test problems, including the “Oscillation of a Non-Equilibrium-Shape Bubble”, “Single- and Multi-mode Rayleigh-Taylor Instability”, “Rising Air Bubble in Water” and “Breakup of Liquid Drop in Gaseous Flow”. For Rayleigh-Taylor instability, the growth rate in the linear regime is in excellent agreement with the analytical solution, and, in the non-linear regime, the penetration rate of the bubble front agrees well with available experimental data. The method is shown to be robust under large density ratios (tested up to 1,000), and large range of flow conditions, from nearly-incompressible to highly supersonic.}, booktitle={17th AIAA Computational Fluid Dynamics Conference}, author={Nourgaliev, R.R. and Dinh, T.N. and Theofanous, T.G.}, year={2005} }
 @article{nourgaliev_sushchikh_dinh_theofanous_2005, title={Shock wave refraction patterns at interfaces}, volume={31}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-24044501960&partnerID=MN8TOARS}, DOI={10.1016/j.ijmultiphaseflow.2005.04.001}, abstractNote={Interactions of shock waves with gas–gas and gas–liquid interfaces (under both slow–fast and fast–slow configurations) are studied using the recently developed Adaptive Characteristics-based Matching (aCBM) method for capturing interfaces in compressible multi-fluid media. First, we verify our approach for the gas–gas case; a class of problems for which a substantial body of knowledge already exists. Then, we consider slow–fast, gas–liquid interfaces under weak shocks, and fast–slow, liquid–gas interfaces under strong shocks. The very high acoustic impedance mismatch situation here creates significant numerical (simulation) and experimental (visualization) difficulties, and the literature for it is meager and sporadic. Compared to gas–gas interfaces we note both similarities and differences. We discuss the sources for these differences, as well as potential implications of generalizing and embedding such results in multi-dimensional simulation schemes towards improving their front-capturing performance.}, number={9}, journal={International Journal of Multiphase Flow}, author={Nourgaliev, R.R. and Sushchikh, S.Y. and Dinh, T.N. and Theofanous, T.G.}, year={2005}, pages={969–995} }
 @inproceedings{sushchikh_dinh_theofanous_2004, title={A numerical study of the shape effect on drag in supersonic low reynolds number (rarefied) flows}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-2942700403&partnerID=MN8TOARS}, DOI={10.2514/6.2004-1063}, abstractNote={The present numerical study is motivated by the analysis of pressure and shear forces that a rarefled supersonic ∞ow exerts on a drop and acts to deform the drop. We use a high-order accurate Cartesian-grid-based numerical scheme and an advanced method for boundary condition treatment to solve the Navier-Stokes equations for high-speed ∞ows around circular and elliptical bodies with difierent aspect ratios that represent difierent stages of the drop deformation. The calculation results depict a strong efiect of the aspect ratio on drag, while predict weaker dependencies of drag on Reynolds and Mach number over the range examined. With the decrease of aspect ratio, the pressure drag increases while the shear drag decreases. Finally, we show that for a flxed Weber number, the corresponding variation of Mach and Reynolds numbers renders minor changes in pressure drag but signiflcantly alter the shear drag.}, booktitle={AIAA Paper}, author={Sushchikh, S.Yu. and Dinh, T.N. and Theofanous, T.G.}, year={2004}, pages={6566–6575} }
 @article{nourgaliev_dinh_theofanous_2004, title={A pseudocompressibility method for the numerical simulation of incompressible multifluid flows}, volume={30}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-3242720707&partnerID=MN8TOARS}, DOI={10.1016/j.ijmultiphaseflow.2004.03.010}, abstractNote={This paper presents an explicit characteristics-based, conservative, finite-difference method for the simulation of incompressible multiphase flows. The method is based on the artificial compressibility concept, extended to variable-density, and uses a time stretching procedure to relieve the acoustic constrain. We take advantage of the algorithmic simplicity and hyperbolicity provided by the artificial compressibility to develop a flow solver that is numerically robust, accurate and effective for massively parallel computations of incompressible multifluid flows. The resulting method, named Numerical Acoustic Relaxation or NAR, is a combination of the AC concept with the Level Set method for interface-capturing and the Ghost-Fluid method to compute flows with multiple, arbitrary density variation, free or stationary interfaces. In this paper we demonstrate convergence and accuracy of the solver by computing such standard test problems as the “Lid-Driven Cavity” and “Doubly Periodic Shear Layer”. Competitiveness with approximate projection, vorticity stream function, pseudospectral, and Lattice Boltzmann Equation is also discussed. In addition, we demonstrate the interface-capturing features of NAR by means of the “simple” “Rayleigh–Taylor” and “Water Column Collapse” problems.}, number={7-8 SPEC. ISS.}, journal={International Journal of Multiphase Flow}, author={Nourgaliev, R.R. and Dinh, T.N. and Theofanous, T.G.}, year={2004}, pages={901–937} }
 @article{theofanous_li_dinh_2004, title={Aerobreakup in rarefied supersonic gas flows}, volume={126}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-11144311824&partnerID=MN8TOARS}, DOI={10.1115/1.1777234}, abstractNote={We present new experimental results on the interfacial instabilities and breakup of Newtonian liquid drops suddenly exposed to rarefied, high-speed (Mach 3) air flows. The experimental approach allows for the first time detailed observation of interfacial phenomena and mixing throughout the breakup cycle over a wide range of Weber numbers. Key findings are that Rayleigh-Taylor instability alone is the active mechanism for freestream Weber numbers as low as 28 for low viscosity liquids and that stripping rather than piercing is the asymptotic regime as We→∞. This and other detailed visual evidence over 26<We<2,600 are uniquely suitable for testing Computational Fluid Dynamics (CFD) simulations on the way to basic understanding of aerobreakup over a broad range of conditions.}, number={4}, journal={Journal of Fluids Engineering, Transactions of the ASME}, author={Theofanous, T.G. and Li, G.J. and Dinh, T.N.}, year={2004}, pages={516–527} }
 @inproceedings{li_dinh_theofanous_2004, title={An experimental study of droplet breakup in supersonic flow: The effect of long-range interactions}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-2942741075&partnerID=MN8TOARS}, booktitle={AIAA Paper}, author={Li, G.J. and Dinh, T.N. and Theofanous, T.G.}, year={2004}, pages={12063–12073} }
 @inproceedings{dinh_tu_theofanous_2004, title={Burnout in high heat flux boiling: The hydrodynaraic and physico-chemical factors}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-2942709672&partnerID=MN8TOARS}, booktitle={AIAA Paper}, author={Dinh, T.N. and Tu, J.P. and Theofanous, T.G.}, year={2004}, pages={1865–1872} }
 @inproceedings{dinh_tu_yang_nourgaliev_theofanous_2004, title={Characterization and predictability of transient heat transfer in an unstably stratified fluid layer during power startup}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85088757090&partnerID=MN8TOARS}, DOI={10.2514/6.2004-2733}, abstractNote={We study transient heat transfer in unstably stratified fluid layers of importance to thermal management of power equipment. A novel experimental approach was developed and used to obtain thermal images of a heater surface during a power startup and convection pattern formation. We use a high-resolution infrared camera to characterize thermal responses of a vapor- deposited nano-film heater. The experiments were analyzed with a computational fluid dynamics code, using different numerical schemes and grid refinements. It was found that the three- dimensional model based on solving Navier-Stokes and energy equation is generally capable of capturing thermal and flow behavior, including pattern formation in unstably stratified fluid layers. It was also found that presence of non-uniformities of boundary condition may explain the early onset of instabilities observed in experiments as compared to predictions by the direct numerical simulation. Implications of the findings for thermal management are discussed.}, booktitle={37th AIAA Thermophysics Conference}, author={Dinh, T.N. and Tu, J.P. and Yang, Y.Z. and Nourgaliev, R.R. and Theofanous, T.G.}, year={2004} }
 @inproceedings{nourgaliev_dinh_theofanous_koning_greenman_nakafuji_2004, title={Direct numerical simulation of disperse multiphase high-speed flows}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-2942741149&partnerID=MN8TOARS}, booktitle={AIAA Paper}, author={Nourgaliev, R.R. and Dinh, T.N. and Theofanous, T.G. and Koning, J.M. and Greenman, R.M. and Nakafuji, G.T.}, year={2004}, pages={10365–10375} }
 @inproceedings{li_nourgaliev_dinh_theofanous_2004, title={Particle-to-particle long range interaction and drag in supersonic flows}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-2942746723&partnerID=MN8TOARS}, DOI={10.2514/6.2004-1064}, booktitle={AIAA Paper}, author={Li, G.J. and Nourgaliev, R.R. and Dinh, T.N. and Theofanous, T.G.}, year={2004}, pages={6604–6614} }
 @inproceedings{dinh_yang_tu_nourgaliev_theofanous_2004, title={Rayleigh-Bénard natural convection heat transfer: Pattern formation, complexity and predictability}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-14844334669&partnerID=MN8TOARS}, booktitle={Proceedings of the 2004 International Congress on Advances in Nuclear Power Plants, ICAPP'04}, author={Dinh, T.N. and Yang, Y.Z. and Tu, J.P. and Nourgaliev, R.R. and Theofanous, T.G.}, year={2004}, pages={1342–1352} }
 @article{nourgaliev_dinh_theofanous_2004, title={The Characteristics-Based Matching (CBM) method for compressible flow with moving boundaries and interfaces}, volume={126}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-11144306362&partnerID=MN8TOARS}, DOI={10.1115/1.1778713}, abstractNote={Recently, Eulerian methods for capturing interfaces in multi-fluid problems become increasingly popular. While these methods can effectively handle significant deformations of interface, the treatment of the boundary conditions in certain classes of compressible flows are known to produce nonphysical oscillations due to the radical change in equation of state across the material interface. One promising recent development to overcome these problems is the Ghost Fluid Method (GFM). The present study initiates a new methodology for boundary condition capturing in multifluid compressible flows. The method, named Characteristics-Based Matching (CBM), capitalizes on recent developments of the level set method and related techniques, i.e., PDE-based re-initialization and extrapolation, and the Ghost Fluid Method (GFM). Specifically, the CBM utilizes the level set function to capture interface position and a GFM-like strategy to tag computational nodes. In difference to the GFM method, which employs a boundary condition capturing in primitive variables, the CBM method implements boundary conditions based on a characteristic decomposition in the direction normal to the boundary. In this way overspecification of boundary conditions is avoided and we believe so will be spurious oscillations. In this paper, we treat (moving or stationary) fluid-solid interfaces and present numerical results for a select set of test cases. Extension to fluid-fluid interfaces will be presented in a subsequent paper.}, number={4}, journal={Journal of Fluids Engineering, Transactions of the ASME}, author={Nourgaliev, R.R. and Dinh, T.N. and Theofanous, T.G.}, year={2004}, pages={586–604} }
 @inproceedings{dinh_tu_theofanous_2004, title={Two-phase natural circulation flow in AP-1000 in-vessel retention-related ULPU-V facility experiments}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-14844322005&partnerID=MN8TOARS}, booktitle={Proceedings of the 2004 International Congress on Advances in Nuclear Power Plants, ICAPP'04}, author={Dinh, T.N. and Tu, J.P. and Theofanous, T.G.}, year={2004}, pages={928–938} }
 @inproceedings{nourgaliev_dinh_theofanous_2003, title={A characteristics-based approach to the numerical solution of the two-fluid model}, volume={2 B}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0346903367&partnerID=MN8TOARS}, DOI={10.1115/fedsm2003-45551}, abstractNote={This paper is concerned with numerical solutions of the two-fluid models of two-phase flow. The two-fluid modeling approach is based on the effective-field description of inter-penetrating continua and uses constitutive laws to account for the inter-field interactions. The effective-field balance equations are derived by a homogenization procedure and known to be non-hyperbolic. Despite their importance and widespread application, predictions by such models have been hampered by numerical pitfalls manifested in the formidable challenge to obtain convergent numerical solutions under computational grid refinement. At the root of the problem is the absence of hyperbolicity in the field equations and the resulting ill-posedness. The aim of the present work is to develop a high-order-accurate numerical scheme that is not subject to such limitations. The main idea is to separate conservative and non-conservative parts, by implementing the latter as part of the source term. The conservative part, being effectively hyperbolic, is treated by a characteristics-based method. The scheme performance is examined on a compressible-incompressible two-fluid model. Convergence of numerical solutions to the analytical one is demonstrated on a benchmark (water faucet) problem.}, booktitle={Proceedings of the ASME/JSME Joint Fluids Engineering Conference}, author={Nourgaliev, R. and Dinh, N. and Theofanous, T.}, year={2003}, pages={1729–1748} }
 @inproceedings{theofanous_li_dinh_2003, title={Aerobreakup in rarefied supersonic gas flows}, volume={2 B}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0347534125&partnerID=MN8TOARS}, booktitle={Proceedings of the ASME/JSME Joint Fluids Engineering Conference}, author={Theofanous, T.G. and Li, G.J. and Dinh, T.N.}, year={2003}, pages={1685–1703} }
 @inproceedings{dinh_li_theofanous_2003, title={An investigation of droplet breakup in a high mach, low Weber number regime}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85088342265&partnerID=MN8TOARS}, DOI={10.2514/6.2003-317}, abstractNote={The paper is concerned with fuel droplet breakup in liquid-fuel Pulse Detonation Engines (PDE). Of particular interest is a high Mach, low Weber number regime that results from the microscopic size of fuel droplets in transonic and supersonic gas flow in detonation engines. We present a new experimental approach to enable characterization of droplet breakup in this novel regime. It is based on a scaling rationale that employs the low density of rarefied gas in experiments to compensate for the microscopic size of fuel droplets in combustors. The paper gives a description of the experimental facility and discusses preliminary results.}, booktitle={41st Aerospace Sciences Meeting and Exhibit}, author={Dinh, T.N. and Li, G.J. and Theofanous, T.G.}, year={2003} }
 @article{sehgal_theerthan_giri_karbojian_willschütz_kymäläinen_vandroux_bonnet_seiler_ikkonen_et al._2003, title={Assessment of reactor vessel integrity (ARVI)}, volume={221}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0037375397&partnerID=MN8TOARS}, DOI={10.1016/S0029-5493(02)00343-6}, abstractNote={The cost-shared project ARVI (assessment of reactor vessel integrity) involves a total of nine organisations from Europe and USA. The objective of the ARVI Project is to resolve the safety issues that remain unresolved for the melt vessel interaction phase of the in-vessel progression of a severe accident. The work consists of experiments and analysis development. Four tests were performed in the EC-FOREVER Programme, in which failure was achieved in-vessels employing the French pressure vessel steel. The tests were analysed with the commercial code ANSYS-Multiphysics, and the codes SYSTUS+ and PASULA, and quite good agreement was achieved for the failure location. Natural convection experiments in stratified pools have been performed in the SIMECO and the COPO facilities, which showed that much greater heat is transferred downwards for immiscible layers or before layers mix. A model for gap cooling and a set of simplified models for the system codes have been developed. MVITA code calculations have been performed for the Czech and Hungarian VVERs, towards evaluation of the in-vessel melt retention accident management scheme. Tests have been performed at the ULPU facility with organised flow for vessel external cooling. Considerable enhancement of the critical heat flux (CHF) was obtained. The ARVI Project has reached the halfway stage. This paper presents the results obtained thus far from the project.}, number={1-3 SPEC.}, journal={Nuclear Engineering and Design}, author={Sehgal, B.R. and Theerthan, A. and Giri, A. and Karbojian, A. and Willschütz, H.G. and Kymäläinen, O. and Vandroux, S. and Bonnet, J.M. and Seiler, J.M. and Ikkonen, K. and et al.}, year={2003}, pages={23–53} }
 @article{dinh_theofanous_2003, title={Nucleation phenomena in boiling}, volume={15}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-56749124910&partnerID=MN8TOARS}, DOI={10.1615/MultScienTechn.v15.i1-4.290}, abstractNote={The mechanisms of phase nucleation are reviewed, starting with the classical theories of homogeneous and heterogenous nucleation. The principle issues in nucleation are addressed (including nucleation on smooth cavity-free surfaces and the role of nano-scale phenomena). It is concluded that nucleation is not well understood and the importance of strict protocols in experiments is stressed.}, number={1-4}, journal={Multiphase Science and Technology}, author={Dinh, T.N. and Theofanous, T.G.}, year={2003}, pages={349–363} }
 @inproceedings{dinh_tu_dinh_theofanous_2003, title={Nucleation phenomena in boiling on nanoscopically smooth surfaces}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84894731207&partnerID=MN8TOARS}, booktitle={41st Aerospace Sciences Meeting and Exhibit}, author={Dinh, T.N. and Tu, J.P. and Dinh, A.T. and Theofanous, T.G.}, year={2003} }
 @article{dinh_nourgaliev_theofanous_2003, title={On the multiscale treatment of multifluid flow}, volume={15}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-52249116021&partnerID=MN8TOARS}, DOI={10.1615/MultScienTechn.v15.i1-4.210}, abstractNote={This contribution surveys the various scales at which multi-phase systems can be modelled (effective field modelling, capturing large scale discontinuities at the largest scale, down to molecular dynamics modelling at the smallest scale) and shows how a multiscale treatment is necessary to capture the important flow features. The multiscale approach is illustrated with several examples.}, number={1-4}, journal={Multiphase Science and Technology}, author={Dinh, T.N. and Nourgaliev, R.R. and Theofanous, T.G.}, year={2003}, pages={275–288} }
 @inproceedings{nourgaliev_dinh_theofanous_2003, title={The 'Characteristics-Based Matching' (CBM) method for compressible flow with moving boundaries and interfaces}, volume={2 B}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0346273024&partnerID=MN8TOARS}, DOI={10.1115/fedsm2003-45550}, abstractNote={Recently, Eulerian methods for capturing interfaces in multi-fluid problems become increasingly popular. While these methods can effectively handle significant deformations of interface, they have been known to produce nonphysical oscillations near material interfaces due to the smeared out density profile and radical change in equation of state across a material interface. One promising recent development to overcome these problems is the ‘Ghost Fluid Method’ (GFM). While being able to produce excellent results for simulation of gas-gas flows, the GFM boundary treatment is unsatisfactory for the case of liquid-liquid or liquid-gas compressible flows. The present study devotes to a new methodology for boundary condition capturing in multi-fluid compressible flows. The method, named ‘Characteristics-Based Matching (CBM)’, capitalizes on the recent development of the level set method and related techniques, i.e., PDE-based re-initialization and extrapolation, and the ‘Ghost Fluid Method’ (GFM). Specifically, the CBM utilizes the level set function to ‘capture’ interface position and a GFM-like strategy to tag computational nodes. In difference to the GFM method, which employs a boundary condition capturing in primitive variables, the CBM method implements boundary conditions based on a characteristic decomposition in the direction normal to the boundary. Since the method allows to avoid over-specification of boundary conditions by respecting the information flow, we believe that the CBM is able to ‘cure’ above-mentioned problems of the GFM boundary condition capturing technique. In this paper, the method’s performance is examined on fluid dynamics problems with stationary and moving boundaries. Numerical results agree well with known analytical or computational solutions and experimental data. Robust and accurate solutions were obtained. In particular, spurious over/under-heating errors, typical for moving boundary treatment by other methods, are essentially eliminated in the CBM solutions.}, booktitle={Proceedings of the ASME/JSME Joint Fluids Engineering Conference}, author={Nourgaliev, R. and Dinh, N. and Theofanous, T.}, year={2003}, pages={1705–1728} }
 @inproceedings{nourgaliev_dinh_sushchikh_yuen_theofanous_2003, title={The characteristics-based matching method for compressible flow in complex geometries}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84894768523&partnerID=MN8TOARS}, booktitle={41st Aerospace Sciences Meeting and Exhibit}, author={Nourgaliev, R.R. and Dinh, T.N. and Sushchikh, S.Y. and Yuen, W.W. and Theofanous, T.G.}, year={2003} }
 @article{nourgaliev_dinh_theofanous_joseph_2003, title={The lattice Boltzmann equation method: Theoretical interpretation, numerics and implications}, volume={29}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0037247762&partnerID=MN8TOARS}, DOI={10.1016/S0301-9322(02)00108-8}, abstractNote={During the last ten years the lattice Boltzmann equation (LBE) method has been developed as an alternative numerical approach in computational fluid dynamics (CFD). Originated from the discrete kinetic theory, the LBE method has emerged with the promise to become a superior modeling platform, both computationally and conceptually, compared to the existing arsenal of the continuum-based CFD methods. The LBE method has been applied for simulation of various kinds of fluid flows under different conditions. The number of papers on the LBE method and its applications continues to grow rapidly, especially in the direction of complex and multiphase media. The purpose of the present paper is to provide a comprehensive, self-contained and consistent tutorial on the LBE method, aiming to clarify misunderstandings and eliminate some confusion that seems to persist in the LBE-related CFD literature. The focus is placed on the fundamental principles of the LBE approach. An excursion into the history, physical background and details of the theory and numerical implementation is made. Special attention is paid to advantages and limitations of the method, and its perspectives to be a useful framework for description of complex flows and interfacial (and multiphase) phenomena. The computational performance of the LBE method is examined, comparing it to other CFD methods, which directly solve for the transport equations of the macroscopic variables.}, number={1}, journal={International Journal of Multiphase Flow}, author={Nourgaliev, R.R. and Dinh, T.N. and Theofanous, T.G. and Joseph, D.}, year={2003}, pages={117–169} }
 @article{nourgaliev_dinh_dinh_haraldsson_sehgal_2003, title={The multiphase Eulerian-Lagrangian transport (MELT-3D) approach for modeling of multiphase mixing in fragmentation processes}, volume={42}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0037285644&partnerID=MN8TOARS}, DOI={10.1016/S0149-1970(03)80006-9}, abstractNote={A new numerical approach for modeling of multiphase mixing during melt jet/droplet fragmentation process is developed. Melt or debris movements are simulated by a particle transport model in a Lagrangian formulation, while thermohydraulic conditions of the surrounding medium are obtained from solution of the Navier-Stokes and energy-conservation equations written in an Eulerian formulation. The Lagrangian and the Eulerian solutions are coupled and advanced in time, with source terms included to model the interactions between the particle and the continuum phases. The method is validated against isothermal solid-sphere, and drop fragmentation experiments. It is found that the model is capable of describing the evolution of the melt-coolant multiphase mixing process with reasonable accuracy. The method is then applied to investigate fragmentation of a continuous jet. Effects of variations in jet/coolant velocities, and of coolant thermophysical properties are analyzed, with particular emphasis on their implications for the fragmentation and mixing processes.}, number={2}, journal={Progress in Nuclear Energy}, author={Nourgaliev, R.R. and Dinh, T.N. and Dinh, A.T. and Haraldsson, H.O. and Sehgal, B.R.}, year={2003}, pages={123–157} }
 @article{sehgal_nourgaliev_dinh_2002, title={Characterization of heat transfer processes in a melt pool convection and vessel-creep experiment}, volume={211}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0036467956&partnerID=MN8TOARS}, DOI={10.1016/S0029-5493(01)00434-4}, abstractNote={The results of an integral experiment on melt pool convection and vessel-creep deformation are presented and analyzed. The experiment is performed on a test facility, named Failure Of REactor VEssel Retention (FOREVER). The facility employs a 1/10-scaled 15Mo3-(German)-steel vessel of 400-mm diameter, 15-mm wall thickness and 750-mm height. A high-temperature (≃1300 °C) oxide melt is prepared in a SiC-crucible placed in a 50 kW induction furnace and is, then, poured into the 1/10th scale vessel. A MoSi2 50 kW electric heater is employed in the melt pool to heat and maintain its temperature at 1200 °C. The vessel is pressurized with argon at the desired pressure. In the FOREVER/C1 experiment, the vessel wall, maintained at about 900 °C and pressurized to 26 bars, was subjected to creep deformation in a 24-h non-stop test. The FOREVER/C1 test is the first integral experiment, in which a decay-heated oxidic naturally-convecting melt pool was maintained in long-term contact with the hemispherical lower head of a pressurized, creeping, steel vessel. A sizeable database was obtained on melt pool temperatures, melt pool energy split, heat transfer rates, heat flux distribution on the melt (crust)–vessel contact surface, vessel temperatures and, in particular the vessel wall creep rate as a function of time. The paper provides information on the FOREVER/C1 measured thermal characteristics and analysis of the observed thermal behavior. The coupled nature of thermal and mechanical processes, as well as the effect of other system conditions (such as depressurization) on the melt pool and vessel temperature responses are analyzed.}, number={2-3}, journal={Nuclear Engineering and Design}, author={Sehgal, B.R. and Nourgaliev, R.R. and Dinh, T.N.}, year={2002}, pages={173–187} }
 @article{nourgaliev_dinh_sehgal_2002, title={On lattice Boltzmann modeling of phase transition in an isothermal non-ideal fluid}, volume={211}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0036467795&partnerID=MN8TOARS}, DOI={10.1016/S0029-5493(01)00435-6}, abstractNote={A new lattice Bolztmann BGK model for isothermal non-ideal fluid is introduced and formulated for an arbitrary lattice, composed of several D-dimensional sublattices. The model is a generalization of the free-energy-based lattice Bolztmann BGK model developed by Swift et al. (1996). We decompose the equilibrium distribution function in the BGK collision operator into ideal and non-ideal parts and employ second-order Chapman–Enskog expansion for treatment of both parts. Expansion coefficients for the non-ideal part are, in general, functions of macroscopic variables, designed to reproduce desired pressure tensor (thermodynamic aspects) and to eliminate the aphysical artifacts in the lattice Bolztmann model. The new model is shown to significantly improve quality of lattice Boltzmann modeling of interfacial phenomena. In the present model, the interface spurious velocity is orders of magnitude lower than that for existing LBE models of non-ideal fluids. A new numerical scheme for treatment of advection and collision operators is proposed to significantly extend stability limits, in comparison to existing solution methods of the ‘master’ lattice Bolztmann equation. Implementation of a ‘multifractional stepping’ procedure for advection operator allows to eliminate severe restriction CFL=1 in traditionally used ‘stream-and-collide’ scheme. An implicit trapezoidal discretization of the collision operator is shown to enable excellent performance of the present model in stiff high-surface-tension regime. The proposed numerical scheme is second order accurate, both in time and space.}, number={2-3}, journal={Nuclear Engineering and Design}, author={Nourgaliev, R.R. and Dinh, T.N. and Sehgal, B.R.}, year={2002}, pages={153–171} }
 @article{theofanous_tu_dinh_dinh_2002, title={The boiling crisis phenomenon part I: Nucleation and nucleate boiling heat transfer}, volume={26}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0036699956&partnerID=MN8TOARS}, DOI={10.1016/S0894-1777(02)00192-9}, abstractNote={This paper (Part I) and the companion paper (Part II, Exp. Therm. Fluid. Sci. 26 (6–7) (2002) 793–810) present results of an experimental study on nucleate pool boiling. The experiments were conducted under highly-controlled conditions, using electrically heated, vapor-deposited sub-micron metallic films. A high-speed, high-resolution infrared camera was used to visualize dynamic thermal patterns on the heater's surface over a broad range of heat fluxes, starting from the onset of nucleation and up to boiling crisis. Both fresh heaters and aged heaters were experimented with. The heaters' surface nanomorphology and chemistry were characterized with atomic force microscopy, scanning electron microscopy, and X-ray diffraction spectroscopy. First-of-a-kind experimental data on nucleation and boiling heat transfer at high heat fluxes are presented, and a stark difference between fresh and aged heaters is revealed. Remarkable are the origin, evolution and dynamics of the heater dryout process (leading to burnout), identified quantitatively and captured in action for the first time.}, number={6-7}, journal={Experimental Thermal and Fluid Science}, author={Theofanous, T.G. and Tu, J.P. and Dinh, A.T. and Dinh, T.N.}, year={2002}, pages={775–792} }
 @article{theofanous_dinh_tu_dinh_2002, title={The boiling crisis phenomenon part II: Dryout dynamics and burnout}, volume={26}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0036699572&partnerID=MN8TOARS}, DOI={10.1016/S0894-1777(02)00193-0}, abstractNote={This is Part II of a two-part paper on the boiling crisis phenomenon. Here we report on burnout experiments conducted on fresh and aged heaters in pool boiling. Critical heat fluxes (CHFs) were found to vary from 50% to 140% of the hydrodynamic limit, previously thought to exist at well-wetting conditions. The burnout events were captured in action (for the first time), using high-speed, high-resolution infrared thermometry. Based on these observations and in conjunction with the levels of CHF reached, we are led to conclude that the phenomenon cannot be (macro)hydrodynamically limited, at least at normal pressure and gravity conditions. Based on infrared thermometry, and aided by X-ray radiography data on void fraction, the case for a scale separation phenomenon in high heat flux pool boiling is argued. This indicates that boiling crisis is controlled by the microhydrodynamics and rupture of an extended liquid microlayer, sitting and vaporizing autonomously on the heater surface. Further, the detailed dynamics of this microlayer, as revealed by our experiments, demonstrates that all previous thermally based models of boiling crisis are inappropriate.}, number={6-7}, journal={Experimental Thermal and Fluid Science}, author={Theofanous, T.G. and Dinh, T.N. and Tu, J.P. and Dinh, A.T.}, year={2002}, pages={793–810} }
 @article{haraldsson_li_yang_dinh_sehgal_2001, title={Effect of solidification on drop fragmentation in liquid-liquid media}, volume={37}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0035393733&partnerID=MN8TOARS}, DOI={10.1007/s002310000097}, number={4-5}, journal={Heat and Mass Transfer/Waerme- und Stoffuebertragung}, author={Haraldsson, H.?. and Li, H.X. and Yang, Z.L. and Dinh, T.N. and Sehgal, B.R.}, year={2001}, pages={417–426} }
 @article{yang_dinh_nourgaliev_sehgal_2001, title={Numerical investigation of boiling regime transition mechanism by a Lattice-Boltzmann model}, volume={204}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0035248476&partnerID=MN8TOARS}, DOI={10.1016/S0029-5493(00)00309-5}, abstractNote={A numerical study has been performed to investigate the hydrodynamic aspects of the pool boilingon horizontal-, vertical- and downward-facing surfaces. The FlowLab code, which is based on a Lattice–Boltzmann (LB) model of two-phase flows, is employed. Macroscopic properties, such as surface tension (σ) and contact angle (β), are implemented through the fluid–fluid (Gσ) and fluid–solid (Gt) interaction potentials. The model is found to express a linear relation between the macroscopic properties (σ, β) and microscopic parameters (Gσ, Gt). The simulation results on bubble departure diameter appear to have the same parametric dependence as the empirical correlation. Hydrodynamic aspects of two-phase flow regime transition mechanism are investigated for different surface–coolant configurations. Results of the LB simulation clearly demonstrate that not only the bubble nucleation site density (related, e.g. to the heater surface condition and heat fluxes), but also the surface position have a profound effect on the flow regime (pool boiling) characteristics. The results of the LB simulation of hydrodynamics of two-phase flow on the horizontal surface provide the pictures quite similar to the experimental observation for saturated pool boiling. Two mechanisms of flow (boiling) regime transition on the vertical surface are predicted for the local bubble coalescence at bubble generation site and the downstream bubble coalescence. On the downward-facing surfaces, friction between bubbles and the surface wall is found to significantly enlarge the bubble size prior the bubble slip upwards. This behavior is responsible for the earlier bubble coalescence, and therefore, lowers the maximum heat removal rate, in a similar regime of nucleate boiling on a downward-facing surface.}, number={1-3}, journal={Nuclear Engineering and Design}, author={Yang, Z.L. and Dinh, T.N. and Nourgaliev, R.R. and Sehgal, B.R.}, year={2001}, pages={143–153} }
 @article{yang_dinh_nourgaliev_sehgal_2001, title={Numerical investigation of bubble growth and detachment by the lattice-Boltzmann method}, volume={44}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0033669318&partnerID=MN8TOARS}, DOI={10.1016/S0017-9310(00)00101-0}, abstractNote={A numerical study has been performed to investigate the characteristics of bubble growth on, and detachment from, an orifice. The FlowLab code, which is based on a lattice-Boltzmann model of two-phase flows, was employed. Macroscopic properties, such as surface tension (σ) and contact angle (β), were implemented through the fluid–fluid (Gσ) and fluid–solid (Gt) interaction potentials. The model was found to possess a linear relation between the macroscopic properties (σ, β) and microscopic parameters (Gσ, Gt). The separate effects of the body force (gravity), gas injection rate, surface tension, and wettability were analyzed for both horizontal and vertical surfaces. It is shown that results of the lattice-Boltzmann modeling exhibit correct parametric dependencies of the departure diameter of bubbles generated on the horizontal surface on the above factors as previously established in experiments. For the case of bubble growth and departure on the vertical surface, the different effects of hydrodynamic parameters, except gas generation rate, were predicted.}, number={1}, journal={International Journal of Heat and Mass Transfer}, author={Yang, Z.L. and Dinh, T.N. and Nourgaliev, R.R. and Sehgal, B.R.}, year={2001}, pages={195–206} }
 @book{haraldsson_kazachkov_dinh_sehgal_2000, title={Analysis of the breakup length of a thin jet penetrating a fluid pool}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-2942534137&partnerID=MN8TOARS}, journal={Advances in Fluid Mechanics}, author={Haraldsson, H.?. and Kazachkov, I.V. and Dinh, T.N. and Sehgal, B.R.}, year={2000}, pages={435–444} }
 @article{dinh_konovalikhin_sehgal_2000, title={Core melt spreading on a reactor containment floor}, volume={36}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0033666565&partnerID=MN8TOARS}, DOI={10.1016/S0149-1970(00)00088-3}, abstractNote={The ex-vessel core melt spreading, cooling and stabilization is proposed for a nuclear power plant containment design. Clearly, the retention and coolability of the decay-heated core debris is very much the focal point in the proposed new and advanced designs so that, in the postulated event of a severe accident, the containment integrity is maintained and the risk of radioactivity releases is eliminated. The work reported here includes three tasks (i) to review related methodology and data base, (ii) to develop the scaling methodology and (iii) to validate the assessment methodology developed by the authors. The study is based on state-of-the-art knowledge of the melt spreading phenomenology, in particular, and, of severe accident phenomenology in general.}, number={4}, journal={Progress in Nuclear Energy}, author={Dinh, T.N. and Konovalikhin, M.J. and Sehgal, B.R.}, year={2000}, pages={405–468} }
 @article{yang_dinh_nourgaliev_sehgal_2000, title={Evaluation of the Darcy's law performance for two-fluid flow hydrodynamics in a particle debris bed using a lattice-Boltzmann model}, volume={36}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0034226551&partnerID=MN8TOARS}, DOI={10.1007/s002310000089}, number={4}, journal={Heat and Mass Transfer/Waerme- und Stoffuebertragung}, author={Yang, Z.L. and Dinh, T.N. and Nourgaliev, R.R. and Sehgal, B.R.}, year={2000}, pages={295–304} }
 @article{yang_dinh_nourgaliev_sehgal_2000, title={Numerical investigation of bubble coalescence characteristics under nucleate boiling condition by a lattice-Boltzmann model}, volume={39}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0033634477&partnerID=MN8TOARS}, DOI={10.1016/S1290-0729(00)00199-9}, abstractNote={A numerical study was performed to investigate the characteristics of bubble growth, detachment and coalescence on vertical, horizontal, and inclined downward-facing surfaces. The FlowLab code, which is based on a lattice-Boltzmann model of two-phase flows, was employed. Macroscopic properties, such as surface tension (σ) and contact angle (β), were implemented through the fluid–fluid (Gσ) and fluid–solid (Gt) interaction potentials. The model predicted a linear relationship between the macroscopic properties (σ,β) and microscopic parameters (Gσ,Gt). The simulation results on bubble departure diameter appear to have the same parametric dependence as the empirical correlation. Hydrodynamic aspects of bubble coalescence are investigated by simulating the growth and detachment behavior of multiple bubbles generated on horizontal, vertical, and inclined downward-facing surfaces. For the case of horizontal surface, three distinct regimes of bubble coalescence were represented in the lattice-Boltzmann simulation: lateral coalescence of bubbles situated on the surface; vertical coalescence of bubbles detached in a sequence from a site; and lateral coalescence of bubbles, detached from the surface. Multiple coalescence was predicted on the vertical surface as the bubble detached from a lower elevation merges with the bubble forming on a higher site. The bubble behavior on the inclined downward-facing surface was represented quite similar to that in the nucleate boiling regime on a downward-facing surface.}, number={1}, journal={International Journal of Thermal Sciences}, author={Yang, Z.L. and Dinh, T.N. and Nourgaliev, R.R. and Sehgal, B.R.}, year={2000}, pages={1–17} }
 @article{dinh_bui_nourgaliev_green_sehgal_1999, title={Experimental and analytical studies of melt jet-coolant interactions: a synthesis}, volume={189}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0032688368&partnerID=MN8TOARS}, DOI={10.1016/S0029-5493(98)00275-1}, abstractNote={Instability and fragmentation of a core melt jet in water have been actively studied during the past 10 years. Several models, and a few computer codes, have been developed. However, there are, still, large uncertainties, both, in interpreting experimental results and in predicting reactor-scale processes. Steam explosion and debris coolability, as reactor safety issues, are related to the jet fragmentation process. A better understanding of the physics of jet instability and fragmentation is crucial for assessments of fuel-coolant interactions (FCIs). This paper presents research, conducted at the Division of Nuclear Power Safety, Royal Institute of Technology (RIT/NPS), Stockholm, concerning molten jet-coolant interactions, as a precursor for premixing. First, observations were obtained from scoping experiments with simulant fluids. Second, the linear perturbation method was extended and applied to analyze the interfacial-instability characteristics. Third, two innovative approaches to computational fluid dynamics (CFD) modeling of jet fragmentation were developed and employed for analysis. The focus of the studies was placed on (a) identifying potential factors, which may affect the jet instability, (b) determining the scaling laws, and (c) predicting the jet behavior for severe accident conditions. In particular, the effects of melt physical properties, and the thermal hydraulics of the mixing zone, on jet fragmentation were investigated. Finally, with the insights gained from a synthesis of the experimental results and analysis results, a new phenomenological concept, named ‘macrointeractions concept of jet fragmentation’ is proposed.}, number={1}, journal={Nuclear Engineering and Design}, author={Dinh, T.N. and Bui, V.A. and Nourgaliev, R.R. and Green, J.A. and Sehgal, B.R.}, year={1999}, pages={299–327} }
 @article{dinh_dinh_nourgaliev_sehgal_1999, title={Investigation of film boiling thermal hydraulics under FCI conditions: results of analyses and a numerical study}, volume={189}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0032641437&partnerID=MN8TOARS}, DOI={10.1016/S0029-5493(98)00276-3}, abstractNote={Film boiling on the surface of a high-temperature melt jet or of a melt particle is one of key phenomena governing the physics of fuel–coolant interactions (FCIs) which may occur during the course of a severe accident in a light water reactor (LWR). A number of experimental and analytical studies have been performed, in the past, to address film boiling heat transfer and the accompanying hydrodynamic aspects. Most of the experiments have, however, been performed for temperature and heat flux conditions, which are significantly lower than the prototypic conditions. For ex-vessel FCIs, liquid subcooling is big and can significantly affect the FCI thermal hydraulics. Presently, there are large uncertainties in predicting natural convection film boiling of subcooled liquids on high-temperature surfaces. In this paper, research conducted at the Division of Nuclear Power Safety, Royal Institute of Technology (RIT/NPS), Stockholm, concerning film boiling thermal hydraulics under FCI condition is presented. Notably, the focuses are placed on the effect of water subcooling, high-temperature steam properties, the radiation heat transfer and mixing zone boiling dynamics on the vapor film characteristics. Numerical investigation is performed using a novel CFD modelling concept named as the local homogeneous slip model (LHSM). Results of the analytical and numerical studies are discussed with regards to boiling dynamics under FCI conditions.}, number={1}, journal={Nuclear Engineering and Design}, author={Dinh, T.N. and Dinh, A.T. and Nourgaliev, R.R. and Sehgal, B.R.}, year={1999}, pages={251–272} }
 @article{sehgal_nourgaliev_dinh_1999, title={Numerical simulation of droplet deformation and break-up by lattice-Boltzmann method}, volume={34}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0032667543&partnerID=MN8TOARS}, DOI={10.1016/s0149-1970(98)00025-0}, abstractNote={In general, a multi-bubble/droplet configuration cannot sustain a steady state using single-component multiphase (SCMP) pseudopotential lattice Boltzmann method (LBM). Our study shows that the unachievable multi-bubble/droplet system is for an unphysical mass transfer, which we call “the big eat the small” – the smaller bubbles/droplets shrink, and eventually disappear while the bigger ones get bigger without a physical coalescence. In our present study, the unphysical mass transfer phenomenon is investigated, and the possible reason is explored. It is found that there is a spurious flow field formed between two bubbles or droplets with different shapes, and such flow field is exactly the transfer of high-density mass. In addition, it is found that the curvatures of the interfaces determine the direction of the spurious flow field, and for the definition of “the big eat the small”, “the big” refers to the interfaces that have larger radii of curvature while “the small” represents the interfaces with smaller radii of curvature. Multi-component multiphase (MCMP) LBM is also tested in this work and it is found to be free of the unphysical mass transfer. Moreover, all the cases show that the most likely reason for the unphysical mass transfer might be the essential attractive interaction forces of the pseudopotential LBM.}, number={4}, journal={Progress in Nuclear Energy}, author={Sehgal, B.R. and Nourgaliev, R.R. and Dinh, T.N.}, year={1999}, pages={471–488} }
 @article{nourgaliev_dinh_sehgal_1997, title={Effect of fluid Prandtl number on heat transfer characteristics in internally heated liquid pools with Rayleigh numbers up to 10<sup>12</sup>}, volume={169}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0031168860&partnerID=MN8TOARS}, DOI={10.1016/S0029-5493(96)01282-4}, abstractNote={This paper presents an analysis of effects of the fluid Prandtl number (Pr) on natural convection heat transfer in volumetrically heated liquid pools. Experimental and computational studies performed in the past are reviewed, with particular emphasis on the analysis of Pr number effects. As a practical exercise, numerical analysis is performed for two-dimensional square, semicircular and elliptical enclosures, and for three-dimensional semicircular and hemispherical cavities, to investigate the physics of the effect of the Pr number on heat transfer in internally heated liquid pools with Rayleigh numbers up to 1012. It was found that the fluid Prandtl number has a small effect on heat transfer in the convection-dominated regions (near the top surface and side walls) of the enclosures. The decrease of the Pr number leads to the decrease of the top and side wall Nusselt (Nu) numbers. The effects of the Pr number on the Nu number at the bottom surface of the enclosures are found to be significant and they become larger with increasing Rayleigh numbers. Two physical mechanisms, i.e. thermal diffusivity and kinematic viscosity phenomena, have been proposed to explain the fluid Prandtl number effects. Calculational results have been used to quantify the significance and the area of influence for each mechanism. Also, strong dependence on the geometry (curvilinearity) of the downward cooled pool surface has been found.}, number={1-3}, journal={Nuclear Engineering and Design}, author={Nourgaliev, R.R. and Dinh, T.N. and Sehgal, B.R.}, year={1997}, pages={165–184} }
 @inproceedings{green_dinh_sehgal_1997, title={Molten-metal jet impingement: insights from experiments and analysis}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0030689335&partnerID=MN8TOARS}, booktitle={International Conference on Nuclear Engineering, Proceedings, ICONE}, author={Green, J.A. and Dinh, T.N. and Sehgal, B.R.}, year={1997}, pages={227} }
 @inproceedings{dinh_dinh_nourgaliev_sehgal_1997, title={Numerical simulation of film boiling heat transfer: Modeling concept and model capabilities}, volume={348}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-5344226287&partnerID=MN8TOARS}, booktitle={American Society of Mechanical Engineers, Heat Transfer Division, (Publication) HTD}, author={Dinh, T.N. and Dinh, A.T. and Nourgaliev, R.R. and Sehgal, B.R.}, year={1997}, pages={1–10} }
 @article{dinh_nourgaliev_sehgal_1997, title={On heat transfer characteristics of real and simulant melt pool experiments}, volume={169}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0031166484&partnerID=MN8TOARS}, DOI={10.1016/s0029-5493(96)01283-6}, abstractNote={This paper presents results of analytical studies on natural convection heat transfer in scaled and/or simulant melt pool experiments related to the pressurized water reactor in-vessel melt retention issue. Specific reactor-scale effects of a large decay-heated core melt pool in the reactor pressure vessel lower plenum are first reviewed, and then the current analytical capability of describing the relevant physical processes in prototypical situations is examined. Experiments and experimental approaches are analyzed by focusing on their ability to represent prototypical situations. Calculations are performed to assess the significance of some selected effects, including variations in melt properties, pool geometry and heating conditions. In the present analysis, Rayleigh numbers are limited to 1012, where uncertainties in turbulence modelling do not override other uncertainties. Calculations are performed to explore limitations of using side wall heating and direct electrical heating. The need for further experimental and analytical efforts is also discussed.}, number={1-3}, journal={Nuclear Engineering and Design}, author={Dinh, T.N. and Nourgaliev, R.R. and Sehgal, B.R.}, year={1997}, pages={151–164} }
 @inproceedings{dinh_green_sehgal_1997, title={On mechanisms that govern the vessel melt source for ex-vessel FCIS}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0030716074&partnerID=MN8TOARS}, booktitle={International Conference on Nuclear Engineering, Proceedings, ICONE}, author={Dinh, T.N. and Green, J.A. and Sehgal, B.R.}, year={1997}, pages={233} }
 @inproceedings{nourgaliev_dinh_sehgal_1997, title={Parametric investigation of a local-homogeneous-slip model of film boiling on horizontal cylinders}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0030655511&partnerID=MN8TOARS}, booktitle={International Conference on Nuclear Engineering, Proceedings, ICONE}, author={Nourgaliev, R.R. and Dinh, T.N. and Sehgal, B.R.}, year={1997}, pages={232} }
 @article{nourgaliev_dinh_sehgal_1997, title={Simulation and analysis of transient cooldown natural convection experiments}, volume={178}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0006800676&partnerID=MN8TOARS}, DOI={10.1016/S0029-5493(97)00177-5}, abstractNote={The characteristics of natural convection heat transfer during transient cooldown in 3-dimensional fluid layers and hemispherical cavity have been investigated by means of a finite-difference numerical method. It was found that the turbulent structure and heat transfer characteristics of the unstably-stratified upper wall region are similar for internal heating (IH) case and transient cooldown (TCD) case, except near the cooled bottom wall of fluid layer, and for a small region (φ≤15°) near the bottom of the hemispherical cavity. For most of the surface area of the hemispherical cavity, there is excellent agreement between the heat fluxes calculated for the IH and the TCD cases. Calculations also showed that pseudosteady-state natural convection (PSSNC) is a better model for simulation of volumetric energy sources.}, number={1}, journal={Nuclear Engineering and Design}, author={Nourgaliev, R.R. and Dinh, T.N. and Sehgal, B.R.}, year={1997}, pages={13–27} }
 @inproceedings{nourgaliev_dinh_sehgal_1997, title={Simulation of multiphase mixing by a particle transport model}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0030684841&partnerID=MN8TOARS}, booktitle={International Conference on Nuclear Engineering, Proceedings, ICONE}, author={Nourgaliev, R.R. and Dinh, T.N. and Sehgal, B.R.}, year={1997}, pages={231} }
 @article{nourgaliev_dinh_1997, title={The investigation of turbulence characteristics in an internally-heated unstably-stratified fluid layer}, volume={178}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0031553171&partnerID=MN8TOARS}, DOI={10.1016/S0029-5493(97)00231-8}, abstractNote={Turbulence characteristics of the hydro- and thermal-fields in an internally-heated horizontal fluid layer are numerically investigated for Rayleigh numbers up to 5 · 108using a finite-difference code for direct numerical simulations. Calculated results indicate significant anisotropic turbulent behaviour and non-equilibrium of turbulent kinetic energy and thermal variance under unstable-stratification conditions. It was found that important turbulence constants are remarkably non-uniformly distributed across the layer and strongly dependent upon Rayleigh and fluid Prandtl numbers. These factors pose the principal difficulty in developing a generic higher order turbulence model for this type of buoyant flows.}, number={3}, journal={Nuclear Engineering and Design}, author={Nourgaliev, R.R. and Dinh, T.N.}, year={1997}, pages={235–258} }
 @article{dinh_nourgaliev_1997, title={Turbulence modelling for large volumetrically heated liquid pools}, volume={169}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0031165347&partnerID=MN8TOARS}, DOI={10.1016/s0029-5493(96)01281-2}, abstractNote={In this paper, the natural convection heat transfer in a volumetrically heated liquid pool under high Rayleigh number (up to 1015) conditions is investigated. The available turbulence modelling techniques are first reviewed, with particular emphasis on selecting models capable of treating the mechanisms of turbulence that are relevant to high Rayleigh number natural convection. As a practical exercise, numerical analyses are performed for experiments that simulate a molten corium pool in the lower head of an externally cooled VVER-440 reactor pressure vessel (COPO) and Steinberner-Reineke experiments in a square cavity. It is shown that standard forms of the low Reynolds number k-ε model fail to describe the turbulent natural convection heat transfer regimes of interest. Phenomenological corrections for the near-wall turbulent viscosity and turbulent Prandtl number, based on the local Richardson number, are proposed to model the stratification-induced non-isotropy of turbulence in the eddy diffusivity approach. With such corrections, a reasonable agreement is achieved with the experimental data (averaged and local heat fluxes) obtained in the Finnish COPO and Steinberner-Reineke experiments, which involve two-dimensional turbulent convection of water at Rayleigh numbers that range from 1012 to 1015. However, it is considered that reliable computations of the reactor conditions in question require at least second-order corrections to the two-equation turbulence models. The physical aspects related to developing such models are also discussed in the present paper.}, number={1-3}, journal={Nuclear Engineering and Design}, author={Dinh, T.N. and Nourgaliev, R.R.}, year={1997}, pages={131–150} }
 @article{nigmatulin_dinh_1996, title={Analysis of major accidents at atomic power stations}, volume={27}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-6544282746&partnerID=MN8TOARS}, number={1}, journal={Heat Transfer Research}, author={Nigmatulin, B.I. and Dinh, T.N.}, year={1996}, pages={201–209} }
 @article{dinh_nigmatulin_nurgaliev_rassokhin_1996, title={Assessment of the thermal load when molten debris interact with a VVER reactor vessel during a severe accident}, volume={43}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-2842511313&partnerID=MN8TOARS}, number={3}, journal={Thermal Engineering}, author={Dinh, T.N. and Nigmatulin, B.I. and Nurgaliev, R.R. and Rassokhin, N.G.}, year={1996}, pages={189–197} }
 @article{dinh_bui_nourgaliev_okkonen_sehgal_1996, title={Modelling of heat and mass transfer processes during core melt discharge from a reactor pressure vessel}, volume={163}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-30244490610&partnerID=MN8TOARS}, number={1-2}, journal={Nuclear Engineering and Design}, author={Dinh, T.N. and Bui, V.A. and Nourgaliev, R.R. and Okkonen, T. and Sehgal, B.R.}, year={1996}, pages={191–206} }
 @inproceedings{dinh_popov_1993, title={Molten corium - reactor vessel interaction: Scaling and other aspects}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0027836643&partnerID=MN8TOARS}, booktitle={American Society of Mechanical Engineers (Paper)}, author={Dinh, T.N. and Popov, A.A.}, year={1993}, pages={1–9} }
 @inproceedings{zemlianoukhin_dinh_egorova_ustinov_khasanov_buchilin_nechaieva_1991, title={Mathematical and experimental modeling of the thermal-hydraulics for PWR reactivity initiated accident simulation}, volume={165}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0025749185&partnerID=MN8TOARS}, booktitle={American Society of Mechanical Engineers, Heat Transfer Division, (Publication) HTD}, author={Zemlianoukhin, V.V. and Dinh, Truc Nam and Egorova, L.A. and Ustinov, A.K. and Khasanov, R.K. and Buchilin, V.A. and Nechaieva, O.A.}, year={1991}, pages={69–74} }