[michaelsmit]

Hello everyone

I would like to solve a equation that looks like this:

ddt(f) + div(F) = k*laplacian(f)

f is a volScalarField
F is a volVectorField and function of f
k is a scalar

How can I solve this in openFoam? Is it like this?

fvScalarMatrix feqn
(
fvm::ddt(f)
+fvm::div(F)
-k*fvm::laplacian(f)
);

solve feqn;

Thanks!

[Bernhard]

Did you try it like this? You can just compile your solver, which then gives you at an error at solve feqn; Afaik it should be solve(feqn); or feqn.solve().

[alberto]

I think you have to write the divergence term as:

fvm::div(F1, f)

where F = F1*f

Best,

[michaelsmit]

Thank you for your replies!

"solve feqn" should be "feqn.solve()" of course, you are right .

But actually I don't get to solve anything yet. I'm still stuck at the div part. I tried fvm::div(F1,f), but I get the error

no matching function for call to ‘div(Foam::volVectorField&, Foam::volScalarField&)’

Should it maybe be fvc::div?

[alberto]

Sorry, I missed the fact F was a volVectorField. If you can assume F lagged, you can use fvc::div(F), which discretises it explicitly.