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-   -   Incompressibility - Ideal Gas (http://www.cfd-online.com/Forums/cfx/24231-incompressibility-ideal-gas.html)

selim July 6, 2007 03:30

Incompressibility - Ideal Gas
 
Hallo, I am performing a CFD with heat transfer. I apply Ideal Gas law. I didnt specify anything about compressibility. Does CFX treat as incompressible or ?

Regards, Selim

opaque July 6, 2007 09:47

Re: Incompressibility - Ideal Gas
 
Dear Selim,

ANSYS CFX does not have an option for Compressibity / Incompressibility? If the material has variable density, it treated as compressible. Otherwise, it is treated as incompressible..

What are you concerned about?

Opaque.


selim July 6, 2007 10:56

Re: Incompressibility - Ideal Gas
 
Hallo, Thanks for the response I want to perform an incompressible transient CFD with heat transfer option. The equations become easier to treat and for my case it is not so critical to take into account the compressibility effects.


Gert-Jan July 6, 2007 18:10

Re: Incompressibility - Ideal Gas
 
You can distinguish with the energy equation:

- isothermal implies no energy equation;

- thermal energy is applicable for heat transfer for low speed application. When you have a material with a variable density, the temperature will influence the density of your gas.

- Total energy is applicable for heat transfer for high speed application. Only use this when compressible effects are relevant (> mach 0.3). When you have a material with a variable density, the temperature will influcene the density of your gas.

So, you need thermal energy as your density changes with temperature and velocities are relatively low.

Gert-Jan

www.bunova.nl


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