@article{srivastava_echekki_2017, title={PARTICLE-FILTER BASED UPSCALING FOR TURBULENT REACTING FLOW SIMULATIONS}, volume={15}, ISSN={["1940-4352"]}, DOI={10.1615/intjmultcompeng.2017017084}, abstractNote={The particle filter is used to couple a coarse-grained (CG) deterministic solution for a reacting flow with a fine-grained (FG) stochastic solution. The proposed method investigates the feasibility of implementing a multiscale approach for turbulent reacting flows based on large-eddy simulation (LES) coupled with a low-dimensional fine-grained stochastic solution for the subfilter scales reaction and transport. In this study, a model for the turbulent transport in the FG solution is implemented using the linear-eddy model (LEM), which combines a deterministic implementation for reaction, diffusion, and large-scale transport with a stochastic implementation for fine-scale transport. The solution for the continuity and momentum (the Burgers' equation) equations are implemented in 1D. The filtered densities obtained through the FG and the CG solutions are combined using the particle filter to obtain an updated density for the coarse solution that combines the effects of heat release (from the FG solution) and flow dynamics (from the CG solution). The results demonstrate that the particle filter may be a viable tool to couple deterministic CG solutions and stochastic FG solutions in reacting flow applications.}, number={1}, journal={INTERNATIONAL JOURNAL FOR MULTISCALE COMPUTATIONAL ENGINEERING}, author={Srivastava, Shubham and Echekki, Tarek}, year={2017}, pages={1–17} }
 @article{srivastava_desai_merchan-merchan_saveliev_2015, title={Volumetric flame synthesis of one-dimensional molybdenum oxide nanostructures}, volume={35}, ISSN={["1873-2704"]}, DOI={10.1016/j.proci.2014.05.044}, abstractNote={A laminar counter-flow diffusion flame formed with methane/acetylene and oxygen enriched-air was used for the controlled synthesis of 1-D molybdenum oxide nanostructures directly in the gas phase. Raw material was introduced into the oxidizer side of the flame in the form of solid molybdenum wires with ∼99% purity. Molybdenum oxide vapors formed in the gas phase were transported by the gas flow in the flame environment possessing strong thermal and chemical gradients. The generated nanostructures were collected thermophoretically from the flame volume. Essential morphological variations of generated nanomaterials were observed depending on sampling position within the flame volume and probe parameters. The mechanism behind the synthesis of the spherical and 1-D nanoforms is analyzed and modeled numerically. The nanorod growth model involves monomer transport, nucleation and growth. The monomer formation is through the oxidation and vaporization of the probe material. The nucleation model is based on the classical nucleation theory. The model predicts the trajectory and growth of the formed nuclei as they are transported in the flame volume. It is considered that the ends of the cylindrical 1-D nanorods grow by the phenomenon of rough growth while the lateral faces exhibit layered growth. The growth model also considers the contribution of the monomers diffusing on the nanoparticle surface as well as the effect of the atoms impinging directly onto the growth sites and compares their relative contributions. The model qualitatively predicts the variation of aspect ratio of the formed nanomaterials with increase of monomer concentration as observed in the experiments.}, journal={PROCEEDINGS OF THE COMBUSTION INSTITUTE}, author={Srivastava, S. and Desai, M. and Merchan-Merchan, W. and Saveliev, A. V.}, year={2015}, pages={2307–2314} }
 @article{srivastava_echekki_2013, title={A novel Kalman filter based approach for multiscale reacting flow simulations}, volume={81}, ISSN={["1879-0747"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84877832954&partnerID=MN8TOARS}, DOI={10.1016/j.compfluid.2013.04.008}, abstractNote={A multi-scale approach for coupling a coarse-grained (CG) deterministic solution for a reacting flow with a fine-grained (FG) stochastic solution is proposed. The model includes a CG solution for the mass density and momentum and a FG solution for the temperature. A model for the turbulent transport in the FG solution is implemented using the linear-eddy model (LEM), which combines a deterministic implementation for reaction, diffusion and large-scale transport with a stochastic implementation for fine-scale transport. A common variable is obtained from these solutions based on a CG density field defined from continuity on the coarse scales and the spatial filtering of the density derived from the state equation in the FG solution. Kalman filtering is used to combine these two solutions. The resulting CG density is both smooth and steered by heat release from the FG solution. The algorithm is demonstrated on a 1D model combining continuity and the Burgers' equation for the CG solution and the temperature equation with heat release for the FG solution. The results establish the feasibility of Kalman filtering in coupling deterministic CG solutions and stochastic FG solutions in reacting flow applications.}, journal={COMPUTERS & FLUIDS}, author={Srivastava, Shubham and Echekki, Tarek}, year={2013}, month={Jul}, pages={1–9} }