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-   -   HELP! TURBULENCE k-e OR k-omega TURBULENCE MODEL? (https://www.cfd-online.com/Forums/fluent/31886-help-turbulence-k-e-k-omega-turbulence-model.html)

 Mirek Kabacinski July 25, 2003 14:11

HELP! TURBULENCE k-e OR k-omega TURBULENCE MODEL?

Hello Fluent Users again? I have one short question (according to my previous e-mail 2 days ago): Is it possible to simulate CORRECT simulation of steady incompressible air flow around circular cylinder with the aid of mentioned k-eps or k-omega turbulence model in FLUENT (v.6.0.20). I can't get correct static pressure distribution on the back side of cylinder (2-D or 3-D). Diameter of cyl=10mm and Re=1E+3 to 1E+5 (in func. of cyl diameter). Can anybody help me? Thanks in advance.

 Guess July 26, 2003 11:34

Re: HELP! TURBULENCE k-e OR k-omega TURBULENCE MOD

I feel the flow will become unsteady at these reynolds - 10^5! Please check it!

 James Date July 26, 2003 13:59

Re: HELP! TURBULENCE k-e OR k-omega TURBULENCE MOD

I've got a feeling that unsteady vortex shedding (Von Karmen vortex street), occurs at a much lower than Rn = 10^5. Best to check in a good fluid dynamics text.

The first thing I think of with regard to problems like these is fine grids and lots of small time steps and a turbulence model which is not k-e, but possibly k-w.

James

 Mirek Kabacinski July 27, 2003 11:45

Re: HELP! TURBULENCE k-e OR k-omega TURBULENCE MOD

Thanks for your help, but it dosn't solved my problem. Have you got any other ideas to solve my problem. Thanks in advance.

 Mark July 30, 2003 22:06

Re: HELP! TURBULENCE k-e OR k-omega TURBULENCE MOD

Hi,

There is a limit for a k-eps or k-omega turbulent model used to predict flow with strong vortex like your case. However RNG-k-eps will be better than k-eps in this case. If it is possible, you can try RSM turbulent model or LES simulation, results will be more close to your experience. Hope it will giave you little help.

Mark

 buffalo August 24, 2003 22:31

Re: HELP! TURBULENCE k-e OR k-omega TURBULENCE MOD

I have met the same problem before. In predicting pressure and heat transfer cofficient on surface cann't get satisfy result.

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