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How to modify gas constant or special heat ratio in CFX-Pre?

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Old   August 24, 2017, 01:58
Default How to modify gas constant or special heat ratio in CFX-Pre?
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xuhaoyang
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I must modify gas constant or specific heat ratio in CFX-Pre.
Because I investigate the effect of fuild property, such as operating characteristics when the gas constant is constant and specific heat ratio is different.
Thanks
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Old   August 24, 2017, 06:33
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If you modify molar mass M, you also modify specific gas constant r (r=R/M), so you modify also heat ratio Cp/Cv. See Mayer's relation for gas (Cp = Cv + r).
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Old   August 24, 2017, 07:49
Default Could I modify directly gas constant or specific heat ratio in CFX-Pre?
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Could I modify directly gas constant or specific heat ratio in CFX-Pre?
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Old   August 24, 2017, 10:22
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You cannot modify the specific heat ratio, nor the gas constant directly in CFX-Pre.

May I ask what is your goal changing the gas constant, and/or the specific heat ratio? It seems you are making an assumption those quantities are used inside the software somehow. From what I understand, they are not used anywhere explicitly.

You can rewrite the fundamentals in reverse

R_gas = R_universal / Molar Mass ---> Molar Mass = R_universal / R_gas which you can change at will

Cp - Cv = R_gas
Cv = Cp / SpecificRatio --> Cp = SpecificRatio * R_gas / (SpecificRatio - 1)

Hope the above helps,
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