[MamboJambo]

Hello to all,


In compressibleInterFoam of OF2006, the temperature equation is defined as:

    fvScalarMatrix TEqn
    (
        fvm::ddt(rho, T) + fvm::div(rhoPhi, T) - fvm::Sp(contErr, T)
      - fvm::laplacian(turbulence.alphaEff(), T)
      + (
             divUp()// - contErr/rho*p
          +  (fvc::ddt(rho, K) + fvc::div(rhoPhi, K))() - contErr*K
        )
       *(
           alpha1()/mixture.thermo1().Cv()()
         + alpha2()/mixture.thermo2().Cv()()
        )
     ==
        fvOptions(rho, T)
    );

Afterwards two functions are called:

    mixture.correctThermo();
     mixture.correct();

The first function will create a he field from the values of pressure and temperature for each phase and call the correct() function.
In the correct() function the temperature is being recalculated from the energy from line 80-88 in the heRhoThermo.C with a Newton-Raphson method [https://caefn.com/openfoam/temperature-calculation]

My question is: If we are already solving for temperature, why do we need to recalculate the values from energy?

Edit:
The temperature used for the calculation is from obtained from the mixture object which will get the temperature field by inheriting from the basicThermo class.

This object has two AutoPtr pointers for each phase. Each of which will create they own temperature field since they inherit from basicThermo. Are the lines 80-88 just updating the temperature values of these fields? By why from energy and not directly from the calculated temperature?

Or am I getting the wrong idea?

[JuRe09]

Hey MamboJambo,


basically I have the same question!


I have to phases (polymer and air) and a modified TEqn.
Now I want to enforce/overwrite the phase temperatures with the resulting T of TEqn! (no recalculation for each phase based on h equation).


Do you have any idea how to do this?

[MamboJambo]

Try to see how to disconnect on line 80-88 in heRhoThermo.C

        

if (this->updateT())
{
     TCells[celli] = mixture_.THE
     (
         hCells[celli],
         pCells[celli],
         TCells[celli]
       );
 }

somewhere in each thermophysicalProperties dictionary, you will have to put:

   
updateT false;

See if it works

[JuRe09]

Originally Posted by MamboJambo

Try to see how to disconnect on line 80-88 in heRhoThermo.C

        

if (this->updateT())
{
     TCells[celli] = mixture_.THE
     (
         hCells[celli],
         pCells[celli],
         TCells[celli]
       );
 }

somewhere in your thermophysicalProperties dictionary, you will have to put:

   
updateT false;

See if it works

Thank you for your advise. i just commented these lines out... then I had a problem with a wrong temperature field to the boundary patches (no influence on the temperature of the BC...). Seemed to be a bug of my version (openFOAM v 1812)...

[mikulo]

Originally Posted by MamboJambo

Hello to all,


In compressibleInterFoam of OF2006, the temperature equation is defined as:

    fvScalarMatrix TEqn
    (
        fvm::ddt(rho, T) + fvm::div(rhoPhi, T) - fvm::Sp(contErr, T)
      - fvm::laplacian(turbulence.alphaEff(), T)
      + (
             divUp()// - contErr/rho*p
          +  (fvc::ddt(rho, K) + fvc::div(rhoPhi, K))() - contErr*K
        )
       *(
           alpha1()/mixture.thermo1().Cv()()
         + alpha2()/mixture.thermo2().Cv()()
        )
     ==
        fvOptions(rho, T)
    );

Afterwards two functions are called:

    mixture.correctThermo();
     mixture.correct();

The first function will create a he field from the values of pressure and temperature for each phase and call the correct() function.
In the correct() function the temperature is being recalculated from the energy from line 80-88 in the heRhoThermo.C with a Newton-Raphson method [https://caefn.com/openfoam/temperature-calculation]

My question is: If we are already solving for temperature, why do we need to recalculate the values from energy?

Edit:
The temperature used for the calculation is from obtained from the mixture object which will get the temperature field by inheriting from the basicThermo class.

This object has two AutoPtr pointers for each phase. Each of which will create they own temperature field since they inherit from basicThermo. Are the lines 80-88 just updating the temperature values of these fields? By why from energy and not directly from the calculated temperature?

Or am I getting the wrong idea?

Hello,

I do have the same question as well. It bothers me because I need to add some source term which will manipulate only the energy equation for the first phase. However, compressibleInterFoam solves the unified T equation which I believe would lead me to wrong solutions. Any thoughts about this?

Regards,
Mike