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-   -   LES problem (http://www.cfd-online.com/Forums/fluent/32181-les-problem.html)

Jose September 21, 2003 19:55

LES problem
 
Hello,

Can I use LES in a steady problem?

Jose

Chetan Kadakia September 25, 2003 04:55

Re: LES problem
 
No. When running LES, it will be an unsteady. I'll explain why later.

thomas September 25, 2003 07:10

Re: LES problem
 
Hey, The turbulence is a 3D and unsteady phenomena. Therefore it does not make a lot of sens to use LES in 2D or in steady case.

thomas

Chetan Kadakia September 26, 2003 03:35

Re: LES problem
 
True it makes sense for 3d. But you can run some 2d analysis with it and get reasonable numbers. But the model has to be 2d in real life, and you it may not be accurate for some of the vortex stretching.

Jose September 26, 2003 13:01

Re: LES problem and VOF
 
Thank you guys,

I am new using this model and I have to study a lot. I have another question I want to use the LES model with the VOF model to predict an interface water-air. The manual says that these two models are incompatible. I don't know why, I think is because the VOF model uses 1st descritisation scheme on time and LES uses second descritisation scheme on time, am I right?

Is correct to use the LES with a 1st descritisation scheme?

Thanks again.

Regards

Jose

thomas September 29, 2003 05:04

Re: LES problem and VOF
 
Hey, I am not an expert but I do not think it is a question of discretization order. First your computational demand (time of calculation) will be infinite using those 2 models. A simple case using separatly LES or VOF already ask a huge time of calculation. Then I DO NOT KNOW your case but LES will solve directly Big structures of the turbulence and model the Small ones. Are you sure it make sens in your case to have such a degree of resolution when you just want to know the interface repartition between the 2 Phases which essentially depends on Big structure of the turbulence. So a simpler Turbulence model would seem enough to get valuable results.

Hope this will give you a further Idea. Regards, thomas.


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