[Storm123]

Hello Everyone,

I am trying to solve this equation using OpenFoam:

dP/dt=z/(∅*P*C ) ∇(P*k/(μ*z) ∇P) ....eq.1

However, it seems there no command to discritize a scalar multiplied by a laplacian.

So I decomposed the equation to the following (d(uv)=udv+vdu):
dP/dt=∇(k/(∅*μ*C) ∇P)-P*k/(μ*z) ∇(z/(∅*P*C))∇P.....eq2

I wrote the second equation as:

volScalarField A = K/PHI/MU/C;

fvSclaraMatrix pEqn
(
fvm::ddt(p)
- fvm::laplacian(A,p)
+(fvc::grad(p)&fvc::grad(zeta/(PHI*p*C)))*K/(MU*zeta)
==
fvOptions(p)
);


So my solver runs, and I can get a solution, however it is a wrong solution. More often than not, I need to have large relaxation numbers to even get a solution. I am new to OpenFoam, so I thought I might ask for help for a way to apply the initial equation 1 without the need to decompose it into equation 2 (It is the second term on the rhs of equation 2 that is causing trouble, so I am not sure about its discritization). Is there a way to multiply a scalar by a laplacian in equation number 1?

Thank you very much, and please bear with me if I made stupid remarks or comments that showed lack of understanding, as I am new.

Thanks.