Analysis of Local Entropy Generation Using Large Eddy Simulation of Turbulent Reacting Flows

2013 ◽  
Author(s):  
Mehdi Safari ◽  
Fatemeh Hadi ◽  
Reza Sheikhi
Keyword(s):  
Large Eddy Simulation ◽  
Entropy Generation ◽  
Reacting Flows ◽  
Turbulent Reacting Flows ◽  
Local Entropy ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Local Entropy Generation

Local Entropy Generation in Large Eddy Simulation of Turbulent Reacting Flows

2017 ◽  
Author(s):  
Mehdi Safari
Keyword(s):  
Large Eddy Simulation ◽  
Entropy Generation ◽  
Reacting Flows ◽  
Chemical Mechanism ◽  
Turbulent Reacting Flows ◽  
Local Entropy ◽  
Source Terms ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Local Entropy Generation

Analysis of local entropy generation is an effective means to investigate sources of efficiency loss in turbulent combustion from the standpoint of the second law of thermodynamics. A methodology, termed the entropy filtered density function (En-FDF), is developed for large eddy simulation (LES) of turbulent reacting flows to include the transport of entropy, which embodies the complete statistical information about entropy variations within the subgrid scale. The modeled En-FDF contains a stochastic differential equation (SDE) for entropy which is solved by a Lagrangian Monte Carlo method. In this study, a numerical study has been done on effectiveness of SDE to model entropy variation using a partially stirred reactor (PaSR). This provides a computationally affordable case to compare different effects of entropy generation source terms and fine tune mixing coefficients. In this equation, turbulent mixing is modeled with Interaction by Exchange with the Mean (IEM). Combustion source terms are provided by direct integration of a GRI3.0 mechanism for methane/air system. Evolution of entropy was calculated from stochastic model and then compared with the one obtained directly by integrating the chemical mechanism. It was shown that results of both calculations have very good agreement versus different mixture fractions.

Analysis of Local Entropy Generation via Large Eddy Simulation of Turbulent Flows

2010 ◽  
Author(s):  
M. Reza H. Sheikhi ◽  
Mehdi Safari ◽  
Hameed Metghalchi
Keyword(s):  
Large Eddy Simulation ◽  
Transport Equation ◽  
Turbulent Flows ◽  
Entropy Generation ◽  
Local Entropy ◽  
Filtered Density Function ◽  
Eddy Simulation ◽  
Entropy Transport ◽  
Large Eddy ◽  
Local Entropy Generation

A novel methodology is developed for local entropy generation analysis of turbulent flows using large eddy simulation (LES). The entropy transport equation is introduced in LES. The filtered form of this equation includes the unclosed subgrid scale entropy generation effects. The closure is based on the filtered density function (FDF) methodology, extended to include the transport of entropy. An exact transport equation is derived for the FDF. The unclosed terms in this equation is modeled by considering a system of stochastic differential equations. LES/FDF is employed to simulate a turbulent shear layer involving transport of mass, energy and entropy. The local entropy generation effects are obtained from the FDF and analyzed. It is shown that the dominant contribution to entropy generation in this flow is due to the combined effects of energy transfer by heat interaction and mass diffusion.

Large Eddy Simulation for Local Entropy Generation Analysis of Turbulent Flows

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
M. R. H. Sheikhi ◽  
Mehdi Safari ◽  
Hameed Metghalchi
Keyword(s):  
Large Eddy Simulation ◽  
Transport Equation ◽  
Turbulent Flows ◽  
Entropy Generation ◽  
Local Entropy ◽  
Filtered Density Function ◽  
Eddy Simulation ◽  
Entropy Transport ◽  
Large Eddy ◽  
Local Entropy Generation

A new methodology is developed for local entropy generation analysis of turbulent flows using large eddy simulation (LES). The entropy transport equation is considered in LES and is solved along with continuity, momentum, and scalar transport equations. The filtered entropy equation includes several unclosed source terms that contribute to entropy generation. The closure is based on the filtered density function (FDF) methodology, extended to include the transport of entropy. An exact transport equation is derived for the FDF. The unclosed terms in this equation are modeled by considering a system of stochastic differential equations (SDEs). The methodology is employed for LES of a turbulent shear layer involving transport of passive chemical species, energy, and entropy. The local entropy generation effects are obtained from the FDF and are analyzed. It is shown that the dominant contribution to entropy generation in this flow is due to combined effects of energy transfer by heat and mass diffusion. The FDF results are assessed by comparing with those obtained by direct numerical simulation (DNS) of the same layer. The FDF predictions show favorable agreements with the DNS data.

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