Incompressible Ideal Gas UDF

inscrutable · October 24, 2022, 14:37

Hi all,

How do you define a different operating pressure for different outlets If an incompressible ideal gas law is used.

My geometry model contains 2 inlets and 2 outlets and each have different fluid.

I'd like to calculate the rho based on the local temperature. I can't use a fixed operating pressure.

Since rho= P_OP/(R/M)*T

I'd like to write a function/expression/UDF to describe:

IF fluid is Water then > the operating pressure is 1 bar

IF fluid is Air then> the operating pressure is 2 bar.

Is this possible?

Any help would be really appreciated!

inscrutable · October 24, 2022, 15:39

Hi guys I made an expression as follows it seems to be right! but Im open to other methods.

(100 [Pa])/ (((R /28.996 [kg/kmol])) *StaticTemperature)

Best

neelcfd · October 26, 2022, 02:54

There's a option of using Incompressible Ideal Gas equation in material property. Make sure you have energy equation on. The density of fluid with only vary with the temperature.

October 24, 2022, 14:37	Incompressible Ideal Gas UDF	#1
inscrutable New Member Join Date: Oct 2022 Posts: 4 Rep Power: 4	Hi all, How do you define a different operating pressure for different outlets If an incompressible ideal gas law is used. My geometry model contains 2 inlets and 2 outlets and each have different fluid. I'd like to calculate the rho based on the local temperature. I can't use a fixed operating pressure. Since rho= P_OP/(R/M)*T I'd like to write a function/expression/UDF to describe: IF fluid is Water then > the operating pressure is 1 bar IF fluid is Air then> the operating pressure is 2 bar. Is this possible? Any help would be really appreciated!

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October 24, 2022, 15:39		#2
inscrutable New Member Join Date: Oct 2022 Posts: 4 Rep Power: 4	Hi guys I made an expression as follows it seems to be right! but Im open to other methods. (100 [Pa])/ (((R /28.996 [kg/kmol])) *StaticTemperature) Best

October 26, 2022, 02:54		#3
neelcfd New Member Neel Join Date: Nov 2018 Posts: 12 Rep Power: 8	There's a option of using Incompressible Ideal Gas equation in material property. Make sure you have energy equation on. The density of fluid with only vary with the temperature.