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Nilanjan Chakraborty - One of the best experts on this subject based on the ideXlab platform.
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Surface Density function evolution and the influence of strain rates during turbulent boundary layer flashback of hydrogen rich premixed combustion
Physics of Fluids, 2020Co-Authors: Umair Ahmed, Nilanjan Chakraborty, Abhishek L Pillai, Ryoichi KuroseAbstract:The statistical behavior of the magnitude of the reaction progress variable gradient [alternatively known as the Surface Density function (SDF)] and the strain rates, which govern the evolution of the SDF, have been analyzed for boundary layer flashback of a premixed hydrogen-air flame with an equivalence ratio of 1.5 in a fully developed turbulent channel flow. The non-reacting part of the channel flow is representative of the friction velocity based Reynolds number Reτ = 120. A skeletal chemical mechanism with nine chemical species and twenty reactions is employed to represent hydrogen-air combustion. Three definitions of the reaction progress variable (RPV) based on the mass fractions of H2, O2, and H2O have been considered to analyze the SDF statistics. It is found that the mean variations of the SDF and the displacement speed Sd depend on the choice of the RPV and the distance away from the wall. The preferential alignment of the RPV gradient with the most extensive principal strain rate strengthens with an increase in distance from the cold wall, which leads to changes in the behaviors of normal and tangential strain rates from the vicinity of the wall toward the middle of the channel. The differences in displacement speed statistics for different choices of the RPV and the wall distance affect the behaviors of the normal strain rate due to flame propagation and curvature stretch. The relative thickening/thinning of the reaction layers of the major species has been explained in terms of the statistics of the effective normal strain rate experienced by the progress variable isoSurfaces for different wall distances and choices of RPVs.
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assessment of algebraic flame Surface Density closures in the context of large eddy simulations of head on quenching of turbulent premixed flames
Combustion Science and Technology, 2017Co-Authors: Jiawei Lai, M Klein, Nilanjan ChakrabortyAbstract:ABSTRACTThe applicability of algebraic large eddy simulation (LES) closures of flame Surface Density (FSD) for head-on quenching of premixed turbulent flames by an isothermal inert wall has been assessed using 3D direct numerical simulations (DNS) data for different values of root-mean-square turbulent velocity fluctuation, Damkohler and Karlovitz numbers. An algebraic FSD closure, which has been reported to perform relatively satisfactorily among several available models, has been considered for this analysis alongside a model, which has recently been used for LES of flame-wall interaction. The applicability of previously proposed near-wall damping factors for flame Surface wrinkling and consumption rate in the context of Reynolds Averaged Navier Stokes (RANS) simulations has also been assessed for LES based on the current a-priori DNS analysis. It has been found that existing models considered for this analysis do not predict the near-wall behavior of the FSD accurately for all cases considered here. Fu...
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a priori and a posteriori analyses of algebraic flame Surface Density modeling in the context of large eddy simulation of turbulent premixed combustion
Numerical Heat Transfer Part A-applications, 2017Co-Authors: Usman Allauddin, M Klein, Michael Pfitzner, Nilanjan ChakrabortyAbstract:ABSTRACTThe flame Surface Density (FSD) based reaction rate closure is one of the most important methodologies of turbulent premixed flame modeling in the context of Large Eddy Simulations (LES). The transport equation for the Favre-filtered reaction progress variable needs closure of the filtered reaction rate and the subgrid scalar flux (SGSF). The SGSF in premixed turbulent flames has both gradient and countergradient components, where the former is typically modeled using eddy diffusivity and the latter can be modeled either on its own or in combination with the filtered reaction rate term using an appropriate wrinkling factor. The scope of the present work is to identify an explicit SGSF closure for the optimum performance in combination with an already established LES FSD model. The performance of different SGSF models for premixed turbulent combustion has been assessed recently by the authors using a Direct Numerical Simulation (DNS) database of freely propagating turbulent premixed flames with a r...
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modeling of the strain rate contribution to the flame Surface Density transport for non unity lewis number flames in large eddy simulations
Combustion Science and Technology, 2014Co-Authors: Mohit Katragadda, Nilanjan ChakrabortyAbstract:The strain rate contribution in the generalized flame Surface Density (FSD) transport equation remains a leading order unclosed source term, which plays a pivotal role in the modeling of transport for all filter widths in the context of large eddy simulations (LES). To date, most FSD-based closures have been proposed for flames without differential diffusion effects of heat and mass, characterized by a global Lewis number equal to unity (i.e., ). The effects of differential diffusion arising due to non-unity Lewis number on the FSD transport have rarely been analyzed in existing literature. In the present analysis, the statistical behaviors of the strain rate term of the FSD transport equation have been analyzed using a DNS database of freely propagating statistically planar turbulent premixed flames with a global Lewis number ranging from 0.34 to 1.2 (i.e., = 0.34–1.2). The FSD strain rate term has been split into components originating from the gradients of Favre-filtered velocity components (i.e., ), s...
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modelling of the tangential strain rate term in the flame Surface Density transport equation in the context of reynolds averaged navier stokes simulations a direct numerical simulation analysis
Mathematical Problems in Engineering, 2014Co-Authors: Mohit Katragadda, Sean P Malkeson, Nilanjan ChakrabortyAbstract:A direct numerical simulation (DNS) database of freely propagating statistically planar turbulent premixed flames with a range of different values of Karlovitz number Ka, turbulent Reynolds number , heat release parameter , and global Lewis number Le has been used to assess the models of the tangential strain rate term in the generalised flame Surface Density (FSD) transport equation in the context of Reynolds averaged Navier Stokes (RANS) simulations. The tangential strain rate term has been split into contributions arising due to dilatation rate and flame normal strain rate (). Subsequently, and () were split into their resolved (i.e., and ()) and unresolved ( and ()) components. Detailed physical explanations have been provided for the observed behaviours of the components of the tangential strain rate term. This analysis gave way to the modelling of the unresolved dilatation rate and flame normal strain rate contributions. Models have been identified for and () for RANS simulations, which are shown to perform satisfactorily in all cases considered, accounting for the variations in Ka, , and Le. The performance of the newly proposed models for the FSD strain rate term have been found to be either comparable to or better than the existing models.
R S Cant - One of the best experts on this subject based on the ideXlab platform.
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turbulent reynolds number dependence of flame Surface Density transport in the context of reynolds averaged navier stokes simulations
Proceedings of the Combustion Institute, 2013Co-Authors: Nilanjan Chakraborty, R S CantAbstract:Abstract The influence of turbulent Reynolds number Re t on the statistical behaviour and modelling of flame Surface Density (FSD) transport has been analysed using a direct numerical simulation (DNS) database of freely propagating turbulent premixed flames with values of Re t ranging from 20 to 100. The variation of Re t is brought about by modifying the Damkohler and Karlovitz numbers independently of each other. The findings indicate that the qualitative behaviour of the various terms of the FSD transport equation remains unaffected by the changes in turbulent Reynolds number, but their relative contributions to the transport of FSD are affected to some extent. The effects of turbulent Reynolds number on the modelling of the turbulent transport term, the tangential strain rate term and the combined propagation and curvature terms are addressed in detail. It is demonstrated that model parameters for the turbulent transport and tangential strain rate term exhibit turbulent Reynolds number dependence for small values of Re t and assume asymptotic values for Re t ⩾ 50 . By contrast, the model parameters for the combined propagation and curvature term are found to be insensitive to the variation of turbulent Reynolds number. Existing models for the turbulent transport term and the tangential strain rate term are modified to account for the observed turbulent Reynolds number dependence.
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effects of turbulent reynolds number on the performance of algebraic flame Surface Density models for large eddy simulation in the thin reaction zones regime a direct numerical simulation analysis
Journal of Combustion, 2012Co-Authors: Mohit Katragadda, Nilanjan Chakraborty, R S CantAbstract:A direct numerical simulation (DNS) database of freely propagating statistically planar turbulent premixed flames with a range of different turbulent Reynolds numbers has been used to assess the performance of algebraic flame Surface Density (FSD) models based on a fractal representation of the flame wrinkling factor. The turbulent Reynolds number Ret has been varied by modifying the Karlovitz number Ka and the Damkohler number Da independently of each other in such a way that the flames remain within the thin reaction zones regime. It has been found that the turbulent Reynolds number and the Karlovitz number both have a significant influence on the fractal dimension, which is found to increase with increasing Ret and Ka before reaching an asymptotic value for large values of Ret and Ka. A parameterisation of the fractal dimension is presented in which the effects of the Reynolds and the Karlovitz numbers are explicitly taken into account. By contrast, the inner cut-off scale normalised by the Zel’dovich flame thickness does not exhibit any significant dependence on Ret for the cases considered here. The performance of several algebraic FSD models has been assessed based on various criteria. Most of the algebraic models show a deterioration in performance with increasing the LES filter width.
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A Priori Assessment of Algebraic Flame Surface Density Models in the Context of Large Eddy Simulation for Nonunity Lewis Number Flames in the Thin Reaction Zones Regime
Journal of Combustion, 2012Co-Authors: Mohit Katragadda, Nilanjan Chakraborty, R S CantAbstract:The performance of algebraic flame Surface Density (FSD) models has been assessed for flames with nonunity Lewis number (Le) in the thin reaction zones regime, using a direct numerical simulation (DNS) database of freely propagating turbulent premixed flames with Le ranging from 0.34 to 1.2. The focus is on algebraic FSD models based on a power-law approach, and the effects of Lewis number on the fractal dimension D and inner cut-off scale ηi have been studied in detail. It has been found that D is strongly affected by Lewis number and increases significantly with decreasing Le. By contrast, ηi remains close to the laminar flame thermal thickness for all values of Le considered here. A parameterisation of D is proposed such that the effects of Lewis number are explicitly accounted for. The new parameterisation is used to propose a new algebraic model for FSD. The performance of the new model is assessed with respect to results for the generalised FSD obtained from explicitly LES-filtered DNS data. It has been found that the performance of the most existing models deteriorates with decreasing Lewis number, while the newly proposed model is found to perform as well or better than the most existing algebraic models for FSD.
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effects of lewis number on flame Surface Density transport in turbulent premixed combustion
Combustion and Flame, 2011Co-Authors: Nilanjan Chakraborty, R S CantAbstract:Abstract The transport of flame Surface Density (FSD) in turbulent premixed flames has been studied using a database obtained from Direct Numerical Simulation (DNS). Three-dimensional freely propagating developing statistically planar turbulent premixed flames have been examined over a range of global Lewis numbers from 0.6 to 1.2. Simplified chemistry has been used and the emphasis is on the effects of Lewis number on FSD transport in the context of Reynolds-averaged closure modelling. Under the same initial conditions of turbulence, flames with low Lewis numbers are found to exhibit counter-gradient transport of FSD, whereas flames with higher Lewis numbers tend to exhibit gradient transport of FSD. Stronger heat release effects for lower Lewis number flames are found to lead to an increase in the positive (negative) value of the dilatation rate (normal strain rate) term in the FSD transport equation with decreasing Lewis number. The contribution of flame curvature to FSD transport is found to be influenced significantly by the effects of Lewis number on the curvature dependence of the magnitude of the reaction progress variable gradient, and on the combined reaction and normal diffusion components of displacement speed. The modelling of the various terms of the FSD transport equation has been analysed in detail and the performance of existing models is assessed with respect to the terms assembled from corresponding quantities extracted from DNS data. Based on this assessment, suitable models are identified which are able to address the effects of non-unity Lewis number on FSD transport, and new or modified models are suggested wherever necessary.
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implications of a flame Surface Density approach to large eddy simulation of premixed turbulent combustion
Combustion and Flame, 2001Co-Authors: Evatt R Hawkes, R S CantAbstract:Abstract Large eddy simulation (LES) is now widely regarded as an improvement on existing computational fluid dynamics (CFD) techniques in addressing classes of combustion problems where traditional CFD approaches have experienced some difficulty 1 , 2 , 3 . This is particularly true in situations where there is significant unsteadiness that is characterized by large-scale flow-flame interactions. The flame Surface Density (FSD) approach to the modeling of premixed turbulent combustion is well established in the context of Reynolds-averaged simulations, and has shown potential as a technique for LES [4] . In this paper, results are presented by using the flame Surface Density model of Hawkes and Cant [4] in a flame propagation test case that further demonstrates the feasibility of the approach. Firstly, the response of the model to variations in turbulence intensity is examined, and an assessment of the relative importance of the source terms in the balance equation for FSD is made. Secondly, it is shown how LES can exploit the effects of large-scale coherent structures in the prediction of FSD through an analysis of the resolved strain source term. Lastly, the model behavior under variations of the filter size is examined. It is an essential but difficult test for FSD models for LES that the results are independent of the filter size. It is shown that the FSD responds to variations in filter size as expected. An increase in filter size results in a decrease in resolved wrinkling, but an increase in sub-grid wrinkling. The net propagation rate of the turbulent flame is shown to be largely independent of the chosen filter size.
M Klein - One of the best experts on this subject based on the ideXlab platform.
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assessment of algebraic flame Surface Density closures in the context of large eddy simulations of head on quenching of turbulent premixed flames
Combustion Science and Technology, 2017Co-Authors: Jiawei Lai, M Klein, Nilanjan ChakrabortyAbstract:ABSTRACTThe applicability of algebraic large eddy simulation (LES) closures of flame Surface Density (FSD) for head-on quenching of premixed turbulent flames by an isothermal inert wall has been assessed using 3D direct numerical simulations (DNS) data for different values of root-mean-square turbulent velocity fluctuation, Damkohler and Karlovitz numbers. An algebraic FSD closure, which has been reported to perform relatively satisfactorily among several available models, has been considered for this analysis alongside a model, which has recently been used for LES of flame-wall interaction. The applicability of previously proposed near-wall damping factors for flame Surface wrinkling and consumption rate in the context of Reynolds Averaged Navier Stokes (RANS) simulations has also been assessed for LES based on the current a-priori DNS analysis. It has been found that existing models considered for this analysis do not predict the near-wall behavior of the FSD accurately for all cases considered here. Fu...
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a priori and a posteriori analyses of algebraic flame Surface Density modeling in the context of large eddy simulation of turbulent premixed combustion
Numerical Heat Transfer Part A-applications, 2017Co-Authors: Usman Allauddin, M Klein, Michael Pfitzner, Nilanjan ChakrabortyAbstract:ABSTRACTThe flame Surface Density (FSD) based reaction rate closure is one of the most important methodologies of turbulent premixed flame modeling in the context of Large Eddy Simulations (LES). The transport equation for the Favre-filtered reaction progress variable needs closure of the filtered reaction rate and the subgrid scalar flux (SGSF). The SGSF in premixed turbulent flames has both gradient and countergradient components, where the former is typically modeled using eddy diffusivity and the latter can be modeled either on its own or in combination with the filtered reaction rate term using an appropriate wrinkling factor. The scope of the present work is to identify an explicit SGSF closure for the optimum performance in combination with an already established LES FSD model. The performance of different SGSF models for premixed turbulent combustion has been assessed recently by the authors using a Direct Numerical Simulation (DNS) database of freely propagating turbulent premixed flames with a r...
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a priori direct numerical simulation assessment of algebraic flame Surface Density models for turbulent premixed flames in the context of large eddy simulation
Physics of Fluids, 2008Co-Authors: Nilanjan Chakraborty, M KleinAbstract:Flame Surface Density (FSD) based reaction rate closure is one of the most important approaches in turbulent premixed flame modeling. The algebraic models for FSD based on power laws often require information about the fractal dimension D and the inner cut-off scale ηi. In the present study, two three-dimensional direct numerical simulation (DNS) databases for freely propagating statistically planar turbulent premixed flames are analyzed among which the flame in one case belongs to the corrugated flamelet (CF) regime, whereas the other falls well within the thin reaction zone (TRZ) regime. It is found that D for the flame in the TRZ regime is greater than the value obtained for the flame in the CF regime. For the flame within the TRZ regime, the fractal dimension is found to be 7/3, which is the same as D for a material Surface in a turbulent environment. For the flame in the CF regime, ηi is found to scale with the Gibson scale, whereas ηi is found to scale with the Kolmogorov length scale for the flame ...
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influence of lewis number on the Surface Density function transport in the thin reaction zone regime for turbulent premixed flames
Physics of Fluids, 2008Co-Authors: Nilanjan Chakraborty, M KleinAbstract:The effects of tangential strain rate and curvature on the Surface Density function (SDF) and on different terms within the SDF transport equation in the thin reaction zone regime are studied for statistically planar turbulent premixed flames with global Lewis numbers Le=0.8, 1.0, and 1.2 by using three-dimensional direct numerical simulations with simplified chemistry. A positive correlation is observed between the SDF and tangential strain rate, and this is explained in terms of the local statistical behaviors of tangential strain rate and dilatation rate. Curvature is shown to affect the SDF through the curvature response of both tangential strain rate and dilatation rate on a given flame isoSurface. The correlation between the curvature and SDF is positive in the Le=0.8 flame and negative in the Le=1.2 flame. The curvature dependence of the SDF is weak in the case of unity Lewis number. Strain rate and curvature are found to have an appreciable effect on different terms of the SDF transport equation. ...
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measurement of flame Surface Density for turbulent premixed flames using plif and dns
Proceedings of the Combustion Institute, 2007Co-Authors: Johan Hult, Nilanjan Chakraborty, Sara Gashi, M Klein, Karl W Jenkins, Stewart Cant, Clemens F KaminskiAbstract:Abstract Results for flame Surface Density (FSD) in premixed turbulent flame kernels have been obtained from OH planar laser induced fluorescence (PLIF) and direct numerical simulations (DNS), and have been compared for similar values of global Lewis number and normalised turbulence intensity. Stoichiometric methane–air and lean hydrogen–air mixtures were studied, and the same post-processing techniques were employed for both experimental and DNS data in order to evaluate FSD statistics from spatial gradients of the reaction progress variable. Full 3D FSD statistics were obtained from the DNS data sets. Also, FSD statistics were obtained from two-dimensional cross-sections extracted from the DNS data sets which were found to be in qualitative agreement with the FSD statistics of PLIF data. The location of maximum FSD within the flame was found to be close to the middle of the flame brush for both methane–air and hydrogen–air flames, and was found to be slightly skewed about the middle of the flame brush for some methane–air flames. The PLIF data for both fuels showed a decrease in the maximum FSD with increasing turbulence intensity. This effect was not observed in the three-dimensional DNS analysis for methane–air flames, but was found to be consistent with both two-dimensional and three-dimensional analysis of the DNS data for hydrogen–air flames. The findings have been compared with the results of other experimental and DNS work reported in the literature and mechanisms have been suggested to explain the observed behaviour.
Mohit Katragadda - One of the best experts on this subject based on the ideXlab platform.
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modeling of the strain rate contribution to the flame Surface Density transport for non unity lewis number flames in large eddy simulations
Combustion Science and Technology, 2014Co-Authors: Mohit Katragadda, Nilanjan ChakrabortyAbstract:The strain rate contribution in the generalized flame Surface Density (FSD) transport equation remains a leading order unclosed source term, which plays a pivotal role in the modeling of transport for all filter widths in the context of large eddy simulations (LES). To date, most FSD-based closures have been proposed for flames without differential diffusion effects of heat and mass, characterized by a global Lewis number equal to unity (i.e., ). The effects of differential diffusion arising due to non-unity Lewis number on the FSD transport have rarely been analyzed in existing literature. In the present analysis, the statistical behaviors of the strain rate term of the FSD transport equation have been analyzed using a DNS database of freely propagating statistically planar turbulent premixed flames with a global Lewis number ranging from 0.34 to 1.2 (i.e., = 0.34–1.2). The FSD strain rate term has been split into components originating from the gradients of Favre-filtered velocity components (i.e., ), s...
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modelling of the tangential strain rate term in the flame Surface Density transport equation in the context of reynolds averaged navier stokes simulations a direct numerical simulation analysis
Mathematical Problems in Engineering, 2014Co-Authors: Mohit Katragadda, Sean P Malkeson, Nilanjan ChakrabortyAbstract:A direct numerical simulation (DNS) database of freely propagating statistically planar turbulent premixed flames with a range of different values of Karlovitz number Ka, turbulent Reynolds number , heat release parameter , and global Lewis number Le has been used to assess the models of the tangential strain rate term in the generalised flame Surface Density (FSD) transport equation in the context of Reynolds averaged Navier Stokes (RANS) simulations. The tangential strain rate term has been split into contributions arising due to dilatation rate and flame normal strain rate (). Subsequently, and () were split into their resolved (i.e., and ()) and unresolved ( and ()) components. Detailed physical explanations have been provided for the observed behaviours of the components of the tangential strain rate term. This analysis gave way to the modelling of the unresolved dilatation rate and flame normal strain rate contributions. Models have been identified for and () for RANS simulations, which are shown to perform satisfactorily in all cases considered, accounting for the variations in Ka, , and Le. The performance of the newly proposed models for the FSD strain rate term have been found to be either comparable to or better than the existing models.
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effects of turbulent reynolds number on the performance of algebraic flame Surface Density models for large eddy simulation in the thin reaction zones regime a direct numerical simulation analysis
Journal of Combustion, 2012Co-Authors: Mohit Katragadda, Nilanjan Chakraborty, R S CantAbstract:A direct numerical simulation (DNS) database of freely propagating statistically planar turbulent premixed flames with a range of different turbulent Reynolds numbers has been used to assess the performance of algebraic flame Surface Density (FSD) models based on a fractal representation of the flame wrinkling factor. The turbulent Reynolds number Ret has been varied by modifying the Karlovitz number Ka and the Damkohler number Da independently of each other in such a way that the flames remain within the thin reaction zones regime. It has been found that the turbulent Reynolds number and the Karlovitz number both have a significant influence on the fractal dimension, which is found to increase with increasing Ret and Ka before reaching an asymptotic value for large values of Ret and Ka. A parameterisation of the fractal dimension is presented in which the effects of the Reynolds and the Karlovitz numbers are explicitly taken into account. By contrast, the inner cut-off scale normalised by the Zel’dovich flame thickness does not exhibit any significant dependence on Ret for the cases considered here. The performance of several algebraic FSD models has been assessed based on various criteria. Most of the algebraic models show a deterioration in performance with increasing the LES filter width.
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A Priori Assessment of Algebraic Flame Surface Density Models in the Context of Large Eddy Simulation for Nonunity Lewis Number Flames in the Thin Reaction Zones Regime
Journal of Combustion, 2012Co-Authors: Mohit Katragadda, Nilanjan Chakraborty, R S CantAbstract:The performance of algebraic flame Surface Density (FSD) models has been assessed for flames with nonunity Lewis number (Le) in the thin reaction zones regime, using a direct numerical simulation (DNS) database of freely propagating turbulent premixed flames with Le ranging from 0.34 to 1.2. The focus is on algebraic FSD models based on a power-law approach, and the effects of Lewis number on the fractal dimension D and inner cut-off scale ηi have been studied in detail. It has been found that D is strongly affected by Lewis number and increases significantly with decreasing Le. By contrast, ηi remains close to the laminar flame thermal thickness for all values of Le considered here. A parameterisation of D is proposed such that the effects of Lewis number are explicitly accounted for. The new parameterisation is used to propose a new algebraic model for FSD. The performance of the new model is assessed with respect to results for the generalised FSD obtained from explicitly LES-filtered DNS data. It has been found that the performance of the most existing models deteriorates with decreasing Lewis number, while the newly proposed model is found to perform as well or better than the most existing algebraic models for FSD.
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modelling of the tangential strain rate term of the flame Surface Density transport equation in the context of reynolds averaged navier stokes simulation
Proceedings of the Combustion Institute, 2011Co-Authors: Mohit Katragadda, Sean P Malkeson, Nilanjan ChakrabortyAbstract:Abstract The modelling of the tangential strain rate term in the Flame Surface Density (FSD) transport equation in the context of Reynolds Averaged Navier–Stokes (RANS) simulations of turbulent premixed combustion has been addressed by a priori analysis of a Direct Numerical Simulation (DNS) database of statistically planar freely propagating flames with wide variations of Damkohler number Da , heat release parameter τ and global Lewis number Le . It has been found that the dilatation rate contribution to the FSD transport strengthens with increasing value of τ and decreasing value of Le . The behaviour of the normal strain rate term shows significant differences in response to Da and Le . It has been found that the normal strain rate contribution to the FSD transport remains a sink term for the flames with high and small values of Da and Le , respectively, where the effects of strain rate induced by heat release a chem overcome the effects of turbulent straining a turb . By contrast, the effects of a turb overcomes the effects of a chem for low Da flames with Le ⩾ 1 , which leads to a positive value of the normal strain rate term towards the unburned gas side, but this term becomes negative towards the burned gas side due to strong a chem overcoming a turb in the regions of intense heat release. The strengthening of the dilatation rate and a chem at small and large values of Le and Da , respectively, is explicitly taken into account to propose new models for the strain rate contributions to the FSD transport. The new model is shown to satisfactorily capture the effects of Damkohler number Da , heat release parameter τ , and global Lewis number Le , on the tangential strain rate term of the FSD transport equation for all the cases considered in this study.
Stacy S Mcgaugh - One of the best experts on this subject based on the ideXlab platform.
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the Surface Density profile of the galactic disk from the terminal velocity curve
The Astrophysical Journal, 2015Co-Authors: Stacy S McgaughAbstract:The mass distribution of the Galactic disk is constructed from the terminal velocity curve and the mass discrepancy–acceleration relation. Mass models numerically quantifying the detailed Surface Density profiles are tabulated. For R0=8 kpc, the models have stellar mass 5<M*<6×10 10 M, scale length 2.0Rd 2.9 kpc, LSR circular velocity 222Θ0233 km s 1 - , and solar circle stellar Surface Density 34Σd(R0) 61 M pc 2 . The present interarm location of the solar neighborhood may have a somewhat lower stellar Surface Density than average for the solar circle. The Milky Way appears to be a normal spiral galaxy that obeys scaling relations like the Tully–Fisher relation, the size–mass relation, and the disk maximality–Surface brightness relation. The stellar disk is maximal, and the spiral arms are massive. The bumps and wiggles in the terminal velocity curve correspond to known spiral features (e.g., the Centaurus arm is a ∼50% overDensity). The rotation curve switches between positive and negative over scales of hundreds of parsecs. The rms amplitude dV dR 14 km s kpc 21 2 1 1 ∣∣ a n» -- , implying that commonly neglected terms in the Jeans equations may be nonnegligible. The spherically averaged local dark matter Density is ρ0,DM≈0.009 M pc 3 (0.34 GeV cm 3 - ). Adiabatic compression of the dark matter halo may help reconcile the Milky Way with the c–V200 relation expected in ΛCDM while also helping to mitigate the too-big-to-fail problem, but it remains difficult to reconcile the inner bulge/bar-dominated region with a cuspy halo. We note that NGC 3521 is a near twin to the Milky Way, having a similar luminosity, scale length, and rotation curve.
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the Surface Density profile of the galactic disk from the terminal velocity curve
arXiv: Astrophysics of Galaxies, 2015Co-Authors: Stacy S McgaughAbstract:The mass distribution of the Galactic disk is constructed from the terminal velocity curve and the mass discrepancy-acceleration relation. Mass models numerically quantifying the detailed Surface Density profiles are tabulated. For $R_0 = 8$ kpc, the models have stellar mass $5 < M_* < 6 \times 10^{10}$ M$_{\odot}$, scale length $2.0 \le R_d \le 2.9$ kpc, LSR circular velocity $222 \le \Theta_0 \le 233$ km s$^{-1}$, and solar circle stellar Surface Density $34 \le \Sigma_d(R_0) \le 61$ M$_{\odot}$ pc$^{-2}$. The present inter-arm location of the solar neighborhood may have a somewhat lower stellar Surface Density than average for the solar circle. The Milky Way appears to be a normal spiral galaxy that obeys scaling relations like the Tully-Fisher relation, the size-mass relation, and the disk maximality-Surface brightness relation. The stellar disk is maximal, and the spiral arms are massive. The bumps and wiggles in the terminal velocity curve correspond to known spiral features (e.g., the Centaurus Arm is a $\sim 50\%$ overDensity). The rotation curve switches between positive and negative over scales of hundreds of parsecs. The rms amplitude $\langle$$|$$dV/dR$$|^2$$\rangle$$^{1/2} \approx 14$ km s$^{-1}$ kpc$^{-1}$, implying that commonly neglected terms in the Jeans equations may be non-negligible. The spherically averaged local dark matter Density is $\rho_{0,DM} \approx 0.009$ M$_{\odot}$ pc$^{-3}$ (0.3 GeV cm$^{-3}$). Adiabatic compression of the dark matter halo may help reconcile the Milky Way with the $c$-$V_{200}$ relation expected in $\Lambda$CDM while also helping to mitigate the too big to fail problem, but it remains difficult to reconcile the inner bulge/bar dominated region with a cuspy halo. We note that NGC 3521 is a near twin to the Milky Way, having a similar luminosity, scale length, and rotation curve.
