flow separation problem

bob

Hi

I am running a simulation of a 3d diffuser of a 4 degree angle.

The geometry has no sharp angles, the inlet BC is a velocity profile with suitable turbulence parameters. The outlet is area averaged static pressure of 0 relative to atmospheric pressure

I have run this with both SST and Reynolds stress models and i allways get flow separation when it should be attached.

Is thee any kind of setting in CFX (i am fairly new) that i may have missed

(have also tried total pressure at inlet with mass flow boundary at outlet and still separation)

Thanks bob