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-   -   Compressible vs incompressible SGS model! (https://www.cfd-online.com/Forums/main/172650-compressible-vs-incompressible-sgs-model.html)

 zhangyan June 2, 2016 21:12

Compressible vs incompressible SGS model!

Hi everyone,
I want to simulate combustion in Internal Combustion Engine with LES.
Now I am trying to implement some SGS models to my code.
But I found many SGS models are suited for incompressible problems.

Fortunately, I found several compressible SGS models:
Code:

compressible SGS models:         compressible Smagorinsky:         [1] Yoshizawa A. Statistical theory for compressible turbulent                                                                    shear flows, with the application to subgrid modeling[J]. Physics                        of Fluids(1958-1988), 1986, 29(7):21522164.         dynamic(Germano)-compressible Smagorinsky:         [2] Moin P, Squires K, Cabot W, et al. A dynamic subgrid-scale                        model for compressible turbulence and scalar transport[J].                        Physics of Fluids A: Fluid Dynamics, 1991, 3(11):2746. DOI:                        10.1063/1.858164.         dynamic(Lilly)-compressible Smagorinsky:         [3] Martνn M P, Piomelli U, Candler G V. Subgrid-Scale Models for                        Compressible Large-Eddy Simulations[J]. Theoretical &         Computational Fluid Dynamics, 2000, 13(5):361376.
I know these compressible SGS models can be used to simulate
compressible problems.
Unfortunately, most of SGS models are incompressible version:
Code:

incompressible SGS models:         Smagorinsky:         [1] Smagorinsky J. General circulation experiments with the primitive equations: I. the basic experiment*[J]. Monthly weather review, 1963, 91(3):99164.         K-eqn:         [2] Yoshizawa A, Horiuti K. A statistically-derived subgrid-scale kinetic energy model for the large-eddy simulation of turbulent flows[J]. Journal of the Physical Society of Japan, 1985, 54(54):28342839.         dynamic(Germano) Smagorinsky:         [3] Germano M, Piomelli U, Moin P, et al. A dynamic subgrid-scale eddy viscosity model[J]. Physics of Fluids A: Fluid Dynamics (1989-1993), 1991, 3(7):17601765.         dynamic(Lilly) Smagorinsky:         [4] Lilly D K. A proposed modification of the Germano subgrid‐scale closure method[J]. Physics of Fluids A Fluid Dynamics, 1992, 4(4):633.         dynamic-K-eqn:         [5] Kim W-W, Menon S. A new dynamic one-equation subgrid-scale model for large eddy simulations[J]. AIAA, Aerospace Sciences Meeting and Exhibit, 33 rd, Reno, NV, 1995.         dynamic-Lagrangian:         [6] Meneveau C, Lund T S, Cabot W H. A Lagrangian dynamic subgrid-scale model of turbulence[J]. Journal of Fluid Mechanics, 1996, 319:353385.         I don't know:         [7] Menon S, Yeung P K, Kim W W. Effect of subgrid models on the computed interscale energy transfer in isotropic turbulence[J]. Computers & Fluids, 1996, 25(2):165180.         WALE:         [8] Nicoud F, Ducros F. Subgrid-scale stress modelling based on the square of the velocity gradient tensor[J]. Flow, turbulence and Combustion, 1999, 62(3):183200.         dynamic structure--1:         [9] Pomraning E, Rutland C J. Dynamic one-equation nonviscosity large-eddy simulation model[J]. AIAA journal, 2002, 40(4):689701.         dynamic structure--2:         [10] Chumakov S G, Rutl C J. Dynamic structure subgrid‐scale models for large eddy simulation[J]. International Journal for Numerical Methods in Fluids, 2005, 47(8‐9):911923.
Question is:
I don't know whether these incompressible models can be used to simulate
compressible problems.

 FMDenaro June 3, 2016 03:43

One of the main difference is in the isotropic term related to div v, for compressible flows you need to supply a model for both isotropic and deviatoric terms.

Have a look here http://www.springer.com/us/book/9789048128181

 zhangyan June 4, 2016 02:42

Quote:
 Originally Posted by FMDenaro (Post 603245) One of the main difference is in the isotropic term related to div v, for compressible flows you need to supply a model for both isotropic and deviatoric terms. Have a look here http://www.springer.com/us/book/9789048128181
Thank you Sir,
I am a first-year graduate student， and I am just start my research.
After reading some papers, I found many people simulate combustion in the internal combustion engine with an incompressible SGS model.
I don't know why.
I think a compressible SGS model is necessary in such simulation.

 FMDenaro June 4, 2016 03:08

it depends on the choice of a low-Mach model

 zhangyan June 4, 2016 03:17

Quote:
 Originally Posted by FMDenaro (Post 603353) it depends on the choice of a low-Mach model
But I never heard Mach number in the cylinder of engine, except for air intake port of engine.
I think the compressibility in the engine is related to the reaction.
Reaction causes the big variation of density.
As far as I know, we didn't mention Mach number in the cylinder combustion simulation.
So, which kind of SGS models should I choose?
Maybe incompressilbe model is OK. But compressible model is better. Do I understand this correctly?

 FMDenaro June 4, 2016 03:31

Quote:
 Originally Posted by zhangyan (Post 603354) But I never heard Mach number in the cylinder of engine, except for air intake port of engine. I think the compressibility in the engine is related to the reaction. Reaction causes the big variation of density. As far as I know, we didn't mention Mach number in the cylinder combustion simulation. So, which kind of SGS models should I choose? Maybe incompressilbe model is OK. But compressible model is better. Do I understand this correctly?

well, no...for the flow in the cylinder you have a fully compressible case...

if you search in google you will find a lot of papers. Try with "LES" and "in-cylinder" words

 zhangyan June 4, 2016 03:43

Quote:
 Originally Posted by FMDenaro (Post 603357) well, no...for the flow in the cylinder you have a fully compressible case... if you search in google you will find a lot of papers. Try with "LES" and "in-cylinder" words
As I mention above, I have found several papers about LES simulation in cylinder simulation, and they all used incompressilbe models.
Such as:
Code:

[1] Jhavar R, Rutland C J. Using Large Eddy Simulations to Study Mixing Effects in Early Injection Diesel Engine Combustion[J]. 2006. DOI: 10.4271/2006-01-0871. [2] Som S, Senecal P K, Laboratory A N, et al. Comparison of RANS and LES Turbulence Models against Constant Volume Diesel Experiments[J]. 2012. [3] Som S, Longman D E, Luo Z, et al. Simulating Flame Lift-Off Characteristics of Diesel and Biodiesel Fuels Using Detailed Chemical-Kinetic Mechanisms and Large Eddy Simulation Turbulence Model[J]. Journal of Energy Resources Technology, 2012, 134(3):189206.
I didn't mean any offense to these authors.
Now I'm quite confused!

 FMDenaro June 4, 2016 03:51

Some studies are related to the valve flowing, without any compression/expansion phase. In such case you can adopt the incompressible model. But if you consider the movement of the piston the compressible effects are relevant.

 zhangyan June 4, 2016 04:17

Quote:
 Originally Posted by FMDenaro (Post 603361) Some studies are related to the valve flowing, without any compression/expansion phase. In such case you can adopt the incompressible model. But if you consider the movement of the piston the compressible effects are relevant.
So, if I want to simulate combustion in engine, I'd better choose the SGS model ,like this :

And,

Am I correct now ?

 FMDenaro June 4, 2016 04:27

If you have combustion I suppose that the SGS model enters into the other equations... for low-Mach model the density variation term can be coupled.

I never worked personally on LES of combustion I suggest following the literature (have a look to the book of Sagaut for reference), your flow problem is often found in the SAE literature

 zhangyan June 4, 2016 04:39

Quote:
 Originally Posted by FMDenaro (Post 603366) If you have combustion I suppose that the SGS model enters into the other equations... for low-Mach model the density variation term can be coupled. I never worked personally on LES of combustion I suggest following the literature (have a look to the book of Sagaut for reference), your flow problem is often found in the SAE literature
Thank you very much!
I have bought that book recently.
And I will read it carefully.

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