Large Eddy Simulation for Prediction of Entropy Generation in a Nonpremixed Turbulent Jet Flame

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.

Download Full-text

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

Volume 5: Energy Systems Analysis, Thermodynamics and Sustainability; NanoEngineering for Energy; Engineering to Address Climate Change, Parts A and B ◽

10.1115/imece2010-39064 ◽

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.

Download Full-text

Large Eddy Simulation for Local Entropy Generation Analysis of Turbulent Flows

Journal of Energy Resources Technology ◽

10.1115/1.4007482 ◽

2012 ◽

Vol 134 (4) ◽

Cited By ~ 8

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.

Download Full-text