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-   -   turbulence modeling error at a stagnation point (http://www.cfd-online.com/Forums/main/11964-turbulence-modeling-error-stagnation-point.html)

erdem August 8, 2006 04:26

turbulence modeling error at a stagnation point
 
hi

I'm studying external aerodynamics of Ahmed Body car geometry. I have used realizable k-eps, SST k-omega and RSM models. in terms of drag coefficient I got similar values with all models. but all of them calculated nearly 1.5-2 times drag at the front of the body (comparing with the original experiments. Realizable k-epsilon has the highest drag on the front.

why does this happen? would you please help me about investigating the greater pressures at the front caused by turbulence modeling? I have to write a discussion about it. this is really important. thanks for you time.

Erdem

Jonas Larsson August 8, 2006 08:47

Re: turbulence modeling error at a stagnation poin
 
The RSM model should not produce too high total pressures in the leading edge region, assuming that you have used it correctly and are not using a near-wall model which does have the leading edge problem that you refer to. The SST and Realizable models might give a bit too high total pressures in the leading edge region. Although these models are much less common to create this problem than for example the standard k-epsilon model.

Have you tried to use different grids and change the extent of your region? To obtain representative drag forces you often need to use a validated type of mesh. It should be extended far away upstream and any side-wall effects must be small.

erdem August 8, 2006 10:28

Re: turbulence modeling error at a stagnation poin
 
thank you for your help Lars but I wonder if I can find further info aboue these models. do you have a reference paper or something about the properties of these turbulence models?

thanks

erdem



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