[adam2008]

Hi,
I have a question about reference pressure. In definition of idea gas, there is a tab of "reference state", and "Air Ideal Gas" in CFX material library uses 14.7psi (1atm) as reference pressure. In domain setting, we also need to set a reference pressure. My question is,
Do I must set this reference pressure in domain setting as 14.7psi also if I use "Air Ideal Gas" as fluid?
I usually set reference pressure in domain setting as "0 psi" for convenience because I am deal with absolute pressure (psia) all the time. I ask because I happend to read one sentence in CFX-help as below
"When using an ideal gas, it is important to set an appropriate reference pressure since some properties depend on the absolute pressure level."

Thanks for your answer

[Shenren_CN]

Originally Posted by adam2008

Hi,
I have a question about reference pressure. In definition of idea gas, there is a tab of "reference state", and "Air Ideal Gas" in CFX material library uses 14.7psi (1atm) as reference pressure. In domain setting, we also need to set a reference pressure. My question is,
Do I must set this reference pressure in domain setting as 14.7psi also if I use "Air Ideal Gas" as fluid?
I usually set reference pressure in domain setting as "0 psi" for convenience because I am deal with absolute pressure (psia) all the time. I ask because I happend to read one sentence in CFX-help as below
"When using an ideal gas, it is important to set an appropriate reference pressure since some properties depend on the absolute pressure level."

Thanks for your answer

You have to, if you want to calculate compressible flow. Because the flow variables depends on the absolute value of the pressure (reference pressure in the domain). I suppose you "usually set reference pressure to 0psi" because you usually run incompressible flow solver, where the reference pressure does not matter at all (meaning it does not affect your velocity field).