Pressure Dependency of Density | Equation of State

dhein · April 29, 2021, 06:36

Hello Community,

actually this might also be a quite general question, I try to get an answer here as I try to model my system with Star-CCM.

I want to compare and validate my FDM C++ Code with a simulation of Star-CCM. In my Code I use an Equation of State for the pressure dependency of the density, from which I can calculate the pressure. In that equation I find the compressibility k.

To compare the results I need a fluid with the same properties in Star. But I can't find the property compressibilty. Also if I look at the density property of Air it says constant.

To validate my Code with the Simulation, am I somehow able to express the Equation of State in a kind of Field Function or is there another way to couple my density with an Equation of State in order to have a fluid that matches my properties?

Kind Regards

fluid23 · April 29, 2021, 08:46

There are various options for EOS of air, including incompressible (constant density) and ideal gas. If those don't satisfy your need, you can always define a user EOS and a custom fluid. I suggest reading the help material, it will tell you everything you need to know.

April 29, 2021, 06:36	Pressure Dependency of Density \| Equation of State	#1
dhein New Member Join Date: Apr 2021 Location: Germany Posts: 8 Rep Power: 5	Hello Community, actually this might also be a quite general question, I try to get an answer here as I try to model my system with Star-CCM. I want to compare and validate my FDM C++ Code with a simulation of Star-CCM. In my Code I use an Equation of State for the pressure dependency of the density, from which I can calculate the pressure. In that equation I find the compressibility k. To compare the results I need a fluid with the same properties in Star. But I can't find the property compressibilty. Also if I look at the density property of Air it says constant. To validate my Code with the Simulation, am I somehow able to express the Equation of State in a kind of Field Function or is there another way to couple my density with an Equation of State in order to have a fluid that matches my properties? Kind Regards

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April 29, 2021, 08:46		#2
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 17	There are various options for EOS of air, including incompressible (constant density) and ideal gas. If those don't satisfy your need, you can always define a user EOS and a custom fluid. I suggest reading the help material, it will tell you everything you need to know.