[Shibi]

Hello to all,


I would like to implement a new Equation of State (EoS) in OpenFOAM 7.


From what I was able to understand, we just need to copy and paste an Equation of State (e.g., perfect Gas) and change it accordingly.



The density (rho) function is known.


The compressibility (psi) should be the derivative of density with respect to pressure (dRho/dp)



However, I am struggling to understand how to define the departure equations for enthalpy, Cp, internal energy, CV and CpMCv.



Are there general equations to define these?


Can anyone complement the procedure to implement a new Equation of State.


At the end, and to use the new EoS, we just need to add a new model in either rhoThermos.C or psiThermos.C depending on the thermophysical model.





Thanks in advance!

[Shibi]

Anyone with some insight on this matter?

[Tobermory]

Look in section 7.1.3 of the user guide:
https://cfd.direct/openfoam/user-gui...hermophysical/
and you'll see that Cp etc are defined by the "thermo" type. The guide tells you that options are hconst, janaf etc. Now go look these up in Doxygen, and you'll see where Cp etc are defined, eg

https://cpp.openfoam.org/v8/janafThe...ce.html#l00171

or

https://cpp.openfoam.org/v8/hConstTh...8H_source.html

You probably need to get your head around each of the components in the thermophysicalProperties dictionary:

thermoType
{
    type            hePsiThermo;
    mixture         pureMixture;
    transport       const;
    thermo          hConst;
    equationOfState perfectGas;
    specie          specie;
    energy          sensibleEnthalpy;
}

before trying to implement your new EOS. Good luck.

[Shibi]

Sorry if this is too basic, but I have been reading through the derivation of rhoSimpleFoam (https://openfoamwiki.net/index.php/RhoSimpleFoam) and was wondering the following:

The density correction is given has

This is true for ideal gases, but if I want to implement something where:


then:

so:



This should mean that I need to create a new pressure equation for this model, correct? Which means that rhoSimpleFoam basiically only work for gas-like EoS, right?