Aye Sandar Kyaw

Hello, Saurabh, thanks for your comment. 
I understand that all the pressures that ANSYS fluent give are gauge pressures.

Moreover, I also set the operating pressure in the operating condition but the problem is when I really want to calculate the absolute pressure based on the results that I obtained (which are gauge pressures), the results (absolute pressures) changed based on the operating pressure I set because even though changing operating pressure didn't change the results of gauge pressure.

In this condition, what should I do in order to calculate the absolute pressure?

Sorry if my question is not clear enough for you. But I am really urgent to solve for this.

Thanks in advance!