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

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.

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