[CFD.MAN]

Hi my friends.
I have prepared a 2D Cfd code to solve duct flow. The inlet is constant velocity and the outlet is no-gradient velocity.
The problem is that the calculated pressure is increasing toward the flow direction. So it creates a flow reveres. from the middle of the duct.
I have checked the code completely, but I think I may have to consider something about the boundary conditions.

Would you please help me for the boundary condition considerations? Shall I set some value for the p or p-prime?

I have changed the inlet-outlet boundaries with each other, and everything got OK. the solution was good.
I wonder why for the first case there is a positive pressure gradient?

Thanks in advance.