Negative pressure in 2D problem

Micgre

Hello world,

I tried to study the pression lost in a valve. To simplify, I tried to work in a 2D problem. You can see my model here :

http://img101.imageshack.us/img101/1...opimagemi4.png

My parameters are : - Air at 25°C - Steady state - Inlet = Pressure at 2200Pa - Outlet = Mass air flow at 0.0009 kg/s - Symetry on both side

In the result, pressure on outlet is around -100000Pa !!!

When I tryed on an 3D model, with same parameters, the result are Ok.

Do you have any idea of this problem on 2D ?

Thanks a lot for your help

Micgre