Compare the pressure of potential flow and a turbulent case of cylinder
 

Hi,

I have a turbulent flow over a cylinder(and an airfoil behind of that) with the initial velocity of 72 m/s .
When we compute the velocity for potential flow, the velocity at the top of cylinder should be 144 and the pressure of -9000 pa.
But in my simulation the pressure at the top of cylinder is about -3000 pa.
I think the differences is considerable.
But in general, when i compare the other results with experimental data,specially the slices over the airfoil, everything is perfect.
Do you know what the problem can be?