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.

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 Prediction of Entropy Generation in a Nonpremixed Turbulent Jet Flame

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Mehdi Safari ◽  
M. Reza H. Sheikhi
Keyword(s):  
Heat Conduction ◽  
Large Eddy Simulation ◽  
Chemical Reaction ◽  
Entropy Generation ◽  
Irreversible Processes ◽  
Filtered Density Function ◽  
Jet Flame ◽  
Eddy Simulation ◽  
Entropy Transport ◽  
Large Eddy

Local entropy generation in a turbulent nonpremixed jet flame (Sandia Flame D) is predicted using large eddy simulation (LES) with inclusion of entropy transport. The filtered form of entropy transport equation contains several unclosed source terms which represent irreversibilities due to viscous dissipation, heat conduction, mass diffusion, and chemical reaction. The subgrid scale (SGS) closure is accounted for by the entropy filtered density function (En-FDF) methodology to include complete statistical information about SGS variation of scalars and entropy. The En-FDF provides closed forms for the chemical reaction effects. The methodology is applied for LES of Sandia Flame D and predictions are validated against experimental data. Entropy statistics are shown to compare favorably with the data. All individual irreversible processes in this flame are predicted and analyzed. It is shown that heat conduction and chemical reaction are the main sources of entropy generation in this flame.

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.

scholarly journals Entropy Transport Equation in Large Eddy Simulation for Exergy Analysis of Turbulent Combustion Systems

Entropy ◽  
2010 ◽  
Vol 12 (3) ◽  
pp. 434-444 ◽  
Author(s):  
Mehdi Safari ◽  
M. Reza H. Sheikhi ◽  
Mohammad Janbozorgi ◽  
Hameed Metghalchi
Keyword(s):  
Large Eddy Simulation ◽  
Transport Equation ◽  
Turbulent Combustion ◽  
Exergy Analysis ◽  
Eddy Simulation ◽  
Entropy Transport ◽  
Large Eddy ◽  
Combustion Systems

Velocity-scalar filtered density function for large eddy simulation of turbulent flows

2003 ◽  
Vol 15 (8) ◽  
pp. 2321-2337 ◽  
Author(s):  
M. R. H. Sheikhi ◽  
T. G. Drozda ◽  
P. Givi ◽  
S. B. Pope
Keyword(s):  
Large Eddy Simulation ◽  
Density Function ◽  
Turbulent Flows ◽  
Filtered Density Function ◽  
Eddy Simulation ◽  
Large Eddy

Entropy Filtered Density Function for Large Eddy Simulation of Turbulent Flows

AIAA Journal ◽  
2015 ◽  
Vol 53 (9) ◽  
pp. 2571-2587 ◽  
Author(s):  
M. R. H. Sheikhi ◽  
M. Safari ◽  
F. Hadi
Keyword(s):  
Large Eddy Simulation ◽  
Density Function ◽  
Turbulent Flows ◽  
Filtered Density Function ◽  
Eddy Simulation ◽  
Large Eddy

Prediction of Local Entropy Generation in Turbulent Combustion Systems

2013 ◽  
Author(s):  
Mehdi Safari ◽  
M. Reza H. Sheikhi
Keyword(s):  
Entropy Generation ◽  
Turbulent Combustion ◽  
Effective Means ◽  
Turbulent Flames ◽  
Turbulent Reacting Flows ◽  
Local Entropy ◽  
Filtered Density Function ◽  
Eddy Simulation ◽  
Combustion Systems ◽  
Local Entropy Generation

Analysis of local entropy generation or exergy destruction is an effective means to investigate sources of efficiency loss to optimize the performance of energy and combustion systems. The local entropy production is predicted using large eddy simulation of turbulent reacting flows. The unclosed entropy generation effects are accounted for by a novel methodology developed based on the filtered density function to embed the transport of entropy. Simulations are conducted of turbulent flames and predictions are validated via experimental data. Sources of irreversibility in turbulent combustion including viscous dissipation, heat conduction, mass diffusion and chemical reaction are predicted and analyzed. The influence of various operating parameters on local entropy generation and the exergetic efficiency of the combustion system is studied.

Velocity filtered density function for large eddy simulation of turbulent flows

2002 ◽  
Vol 14 (3) ◽  
pp. 1196-1213 ◽  
Author(s):  
L. Y. M. Gicquel ◽  
P. Givi ◽  
F. A. Jaberi ◽  
S. B. Pope
Keyword(s):  
Large Eddy Simulation ◽  
Density Function ◽  
Turbulent Flows ◽  
Filtered Density Function ◽  
Eddy Simulation ◽  
Large Eddy
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