please tell me how to get relative pressure, i mean the solution or the formula calculation. and the outlet pressure shown in a straight line that mean all the point and the outlet have same value of pressure. can u give me your mail address.

For incompressible flow simulation, the relative pressure can be considered as the difference from the given(or assumed) value at the given point. Given point might be arbitrary. That is, if you know the pressure at the outlet, you can add the pressure difference between the outlet(where you know the pressure) and the each point, and you can obtain the real pressure.

Example :

- You know outlet pressure, say 101325 Pa

- Outlet pressure of CFD result, say -100Pa

- CFD result for the pressure at the certain point, say -50 Pa.

Don't stick at the value of -100 or -50, You can interprete the result as, presuure at the outlet is 101325Pa(which you have information) and the pressure at the certain point is 101325-(-50)=101375 Pa.

Sincerely, Jinwook