i ask that if i get a positive pressure grident that mean that i will must have flow separation .contact me on my email yelhasdi@yahoo.com thsnks

an adverse pressure gradient i.e. when the flow is decelerating will promote separation either when the boundary layer is laminar or turbulent depending on ho adverse the effects are. But I wouldnt say that you have to have separation, just that the conditions are becoming favourable towards it!

Hi there,

To justify flow separation, you should compute the local friction coefficient and find a negative value.

Sincerely,

Frederic Felten.