Updating thermophysical properties with temperature

mohmmad994 · May 18, 2019, 04:09

how is it possible to write a combustion solver which uses Teqn to solve energy and then for upgrading thermo library what should i do ? i mean the line thermo.correct(); looks to work with changing sensible enthalpy and if enthalpy is not changing thermo lib wouldnt get updated therefore rho=thermo.rho() wouldnt solve the prfect gas formula with the new temperature and rho wouldnt solve correctly.
so my question is in what way i can update thermo lib, only with temperature so i could be able to use it in my solver to find new amount of viscousity and rho according to the temperature?

Thanks ;

raumpolizei · May 20, 2019, 05:30

Hey mohmmad994,

to my knowledge, there is no thermo class relying on a temperature variable being solved. A possible workaround ("hack") would be to calculate the energy variable based on the temperature after solving your temperature equation, but before calling thermo.correct() in your solver. The internal energy or enthalpy is used in the thermo.correct() function to first compute a temperature prior to updating all internal and boundary fields (take for example a look at the hePsiThermo class, more specifically at the correct() and calculate() functions). The more complicated way would be to write an own class that handles your specific issue. Hope this helps.

Cheers
RP

PS: The energy variable can be for example computed if the mixture, pressure and temperature are known in a certain cell via the cellmixture(label celli) and HE(scalar p,scalar T) function (as used in the hePsiThermo<...>::calculate() function).

May 18, 2019, 04:09	Updating thermophysical properties with temperature	#1
mohmmad994 New Member Mohammad Join Date: Mar 2019 Posts: 2 Rep Power: 0	how is it possible to write a combustion solver which uses Teqn to solve energy and then for upgrading thermo library what should i do ? i mean the line thermo.correct(); looks to work with changing sensible enthalpy and if enthalpy is not changing thermo lib wouldnt get updated therefore rho=thermo.rho() wouldnt solve the prfect gas formula with the new temperature and rho wouldnt solve correctly. so my question is in what way i can update thermo lib, only with temperature so i could be able to use it in my solver to find new amount of viscousity and rho according to the temperature? Thanks ;

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May 20, 2019, 05:30		#2
raumpolizei Member Join Date: Dec 2018 Location: Darmstadt, Germany Posts: 87 Rep Power: 7	Hey mohmmad994, to my knowledge, there is no thermo class relying on a temperature variable being solved. A possible workaround ("hack") would be to calculate the energy variable based on the temperature after solving your temperature equation, but before calling thermo.correct() in your solver. The internal energy or enthalpy is used in the thermo.correct() function to first compute a temperature prior to updating all internal and boundary fields (take for example a look at the hePsiThermo class, more specifically at the correct() and calculate() functions). The more complicated way would be to write an own class that handles your specific issue. Hope this helps. Cheers RP PS: The energy variable can be for example computed if the mixture, pressure and temperature are known in a certain cell via the cellmixture(label celli) and HE(scalar p,scalar T) function (as used in the hePsiThermo<...>::calculate() function).