hi all

I'd like to simulate a typical problem: a car in a wind tunnel, to get correlation with real tests.

I've read many articles that say the BC type to apply for the top and external side walls is the symmetry one. But why??? In a real wind tunnel, the top and side walls are not moving and they (unfortunately) interfere with the tested model: the properties of symmetry BC (all gradients = 0, I guess) are thus not always verified. Shouldn't be more appropriate to simply use stationnary walls?

Please give me your ideas.

regards

the wind tunnels they may be very large such that the interaction of the flow is negligible and the gradients will be zero so i think symmetry conditions are perfect.

If you belive that the tunnel walls influence the flow arround the car you should definetelly use stationary wals with (for example) wall functions. But in most applications the walls are far enough from the model so that they don't influence is (at least it should be so). Then you can use symmetry which is in essence wall with free slip condition. This will symplify your simulation and decrease comp. time.

by MATEUS

OK, this is the confirmation I neeeded ;o))) I thank you both