[Benben]

Hello, i am trying to modify reactingFoam in openFoam 6.0 in order to solve rho, then calculate p=f(rho,T).

I want to make a compressible solver with gravity and species transport (+ some annoying specific things). As I am not very comfortable with the pressure equation (to add a mass source term is painfull), i want to solve rho, and calculate p with the perfect gas equation.

I modified the main loop as follow:

while (pimple.loop())
{
    while (pimple.correct())
    {
        #include "./rhoEqn.H"
        Info << rho << endl;//display for debug
        scalar M = thermo.composition().W(0);//The molar mass of the mixture
        p = rho/(psi*M);//P = rho*R*T/M = C*R*T = n*R*T/V
        p.correctBoundaryConditions();
        #include "./UEqn.H"
    }
    #include "compressibleContinuityErrs.H"
    #include "./YEqn.H"
    #include "./EEqn.H"
    if (pimple.turbCorr())
    {
        turbulence->correct();
    }
}

Here are my two problems:

• I have no boundary condition on rho (they are defined for p only), what happens when i solve rho ? Can i correct rho at the boundary using the boundary conditions applied to p ?
• Why is my rho value reseted ? During the pimple.correct loop, rho is calculated, bu on paraview rho is always the same. Is it due to the thermo.correct() in EEqn.H ?

[Benben]

Actually the pressure should be calculated as:

p = rho/psi

Because psi seems to be M/(R*T).

I tried to solve rho without applying any boundary conditions, and then correcting the density at the boundary using the value of the pressure at the boundary. But this obviously didnt work, for example i have flows through walls.

[Benben]

It seems that to solve this correctly i would have to use some boundary conditions on rho instead of p, which is very unpractical. (fixed pressure outlet needs a conversion using ideal gas law for example).
I will stick to presure based equations.