What kind of model are you referring to, and where on the model did you measure the static pressure?  Surface pressure on the model is not necessarily going to be the same as the freestream pressure, due to convective acceleration.  If you have a Pitot-static tube, measure the dynamic pressure with that; otherwise, do you have any pressure taps on the walls of the tunnel itself?  If you do, you can measure the static pressure on the wall of the settling chamber and on the wall of the test section and back out the freestream velocity that way.

Hi

I am investigating air movement inside a room included a wind catcher. I've measured the static pressure of inner walls Also by pitot tube pressure of free stream in test section has been measured. Since the fan is located after model (down stream) there is a suction in pressure outlet. I am not sure for pressure outlet which value should be used. while the pressure gauge is 0 it gives the wrong results .

Are you using the same flow profile (measured in the wind tunnel) for your CFD inlet conditions?

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According to the results of PIV measurement and records of pitot tube and whatever I have monitored in fluent, Velocities before the inlet of wind catcher are same but inside the model and after that are not. 

I've got another question, To monitor the static pressure on the walls of model which type of report is suitable? I have used "Area-Weighted Average" type but I'm not sure if it's correct or not.

Which turbulence model are you using? How did you mesh the internal of the model?

Compare the surface pressure coefficient Cp instead.

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Dear John

I use K-E realizable model and structure mesh with good density near the walls.

I check the Cp plot along the direction which all pressure taps in experiment are lead.