@article{ranganath_echekki_2009, title={ODT Closure with Extinction and Reignition in Piloted Methane-Air Jet Diffusion Flames}, volume={181}, ISSN={["1563-521X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70349196281&partnerID=MN8TOARS}, DOI={10.1080/00102200802529993}, abstractNote={A novel tabulation procedure for reactive scalar statistics based on the one-dimensional turbulence (ODT) is implemented to study extinction and reignition in piloted methane-air jet diffusion flames. The formulation is based on constructing the scalar statistics from stand-alone temporal jet simulations using ODT. The statistics are correlated in terms of two parameters based on a single transported variable: the mean mixture fraction, which measures the extent of mixing between the fuel and oxidizer streams, and the centerline mixture fraction, which measures the extent of entrainment into the fuel jet or the jet evolution downstream. The evolution of momentum and passive scalars is computed using a Reynolds-Averaged Navier-Stokes (RANS) formulation, which uses the 2D table for look-up of the mean density. Other reactive scalars' profiles are obtained from the 2D table and the computed momentum and scalar fields from RANS. Comparison of the computed and the experimental statistics for momentum and scalars shows that the tabulation scheme along with the RANS model yields reasonable predictions of the processes of extinction and reignition in piloted jet diffusion flames.}, number={4}, journal={COMBUSTION SCIENCE AND TECHNOLOGY}, author={Ranganath, Bhargav and Echekki, Tarek}, year={2009}, pages={570–596} }
@article{ranganath_echekki_2008, title={One-dimensional turbulence-based closure with extinction and reignition}, volume={154}, ISSN={["1556-2921"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-44449140442&partnerID=MN8TOARS}, DOI={10.1016/j.combustflame.2008.03.020}, abstractNote={Scalar statistics from stand-alone one-dimensional turbulence (ODT) simulations are constructed to develop a doubly conditioned table based on the mixture fraction and temperature for the prediction of extinction and reignition in piloted methane–air jet diffusion flames. The ODT-based closure approach is formulated to predict scalar statistics coupled with the Reynolds-averaged Navier–Stokes (RANS) approach. Comparison with experimental correlations of reactive scalars with the two conditioning variables show that double conditioning may be adequate to prescribe scalar statistics in the jet diffusion flames. The results also show that the ODT model may be used to construct these statistics. The 2D conditioning table is coupled with RANS to compute Sandia flames D, E, and F, which exhibit increasing rates of extinction followed by reignition as the Reynolds numbers are increased. The coupling also requires the transport of the means and variances of the mixture fraction and temperature. Closure terms in the temperature mean and variance equations are obtained by using the 2D table for reaction source terms and by assuming a presumed PDF shape for the temperature PDF. Comparisons show adequate predictions of axial and radial profiles of the mixture fraction, the streamwise velocity, and the reactive scalars for flames D and E and mixed results for flame F. Nonetheless, qualitative trends of increasing the jet Reynolds numbers resulting in more pronounced extinctions are obtained with the RANS-ODT approach. The discrepancy between computation and experiment may be attributed primarily to the closure for the temperature and its variance and to the presumed PDF shape for the temperature.}, number={1-2}, journal={COMBUSTION AND FLAME}, author={Ranganath, Bhargav and Echekki, Tarek}, year={2008}, month={Jul}, pages={23–46} }
@article{ranganath_echekki_2006, title={On the role of heat and mass transport during the mutual annihilation of two premixed propane-air flames}, volume={49}, ISSN={["1879-2189"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33750358100&partnerID=MN8TOARS}, DOI={10.1016/j.ijheatmasstransfer.2006.05.029}, abstractNote={Abstract The unsteady process of mutual annihilation of two stoichiometric propane–air flames in one dimension is investigated numerically in the presence of preferential (the diffusion of heat relative to mass diffusion of species) and differential diffusion (the relative mass diffusions of species) effects. These effects are found during the early stages of mutual annihilation, corresponding to preheat layers’ interactions, as well as during the merger of the reaction layers. The diffusive mobility of heat relative to the reactants results in the preheating of the reactants and associated increases in the rates of reactants’ consumption. These rates are sustained during the merger of the reaction layers due to the relative mobility of the secondary fuels, especially H 2 , which results in the build-up of radicals in the reaction zone prior to the completion of the mutual annihilation process. Preferential and differential diffusion effects also result in the formation of products of incomplete combustion at the end of this process.}, number={25-26}, journal={INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER}, author={Ranganath, Bhargav and Echekki, Tarek}, year={2006}, month={Dec}, pages={5075–5080} }
@article{ranganath_echekki_2006, title={One-Dimensional Turbulence-based closure for turbulent non-premixed flames}, volume={6}, ISSN={["1741-5233"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33845486306&partnerID=MN8TOARS}, DOI={10.1504/PCFD.2006.010966}, abstractNote={A new One-Dimensional Turbulence (ODT) based closure model for turbulent non-premixed flames is proposed. The model is based on the tabulation of scalar statistics based on two parameters, which measure the extent of mixing and entrainment. The table is generated using different realisations of stand-alone ODT simulations of turbulent jet diffusion flames. The table look-up process is coupled with a Reynolds-Averaged Navier-Stokes (RANS) computation. The scope of the ODT formulation is to predict thermo-chemical scalars statistics in sample space; while its coupling with RANS reproduces these statistics in 3D space. The resulting formulation yields reasonably good agreement with experimental data.}, number={7}, journal={PROGRESS IN COMPUTATIONAL FLUID DYNAMICS}, author={Ranganath, Bhargav and Echekki, Tarek}, year={2006}, pages={409–418} }
@article{ranganath_echekki_2005, title={Effects of preferential and differential diffusion on the mutual annihilation of two premixed hydrogen-air flames}, volume={9}, ISSN={["1741-3559"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-27844561696&partnerID=MN8TOARS}, DOI={10.1080/13647830500294006}, abstractNote={The unsteady process of upstream head-on quenching of two laminar premixed hydrogen–air flames at different equivalence ratios in one dimension is investigated numerically in the presence of preferential and differential diffusion effects. Important chemical and transport characteristics of the mutual annihilation process are studied during the two primary stages of upstream mutual annihilation, preheat layers' and reaction layers' interactions. Because of the diffusive mobility of the fuel, hydrogen, relative to heat and the oxidizer, preferential and differential diffusion effects result in a shift in the equivalence ratio in the reaction zone to leaner conditions. This shift, in turn, affects the subsequent reaction layers' interactions through qualitative and quantitative changes in the rates of reactants' consumption and radicals' production. Another consequence of this shift is the presence of excess and ‘unburnt’ fuel or oxidizer at the end of the mutual annihilation process. The process of mutual annihilation occurs over time scales that are significantly shorter than characteristic residence times associated with flames.}, number={4}, journal={COMBUSTION THEORY AND MODELLING}, author={Ranganath, B and Echekki, T}, year={2005}, month={Nov}, pages={659–672} }