[cgerrity]

Hello,

What is the best way to define a *fixed* space (volume) charge density in OpenFOAM? The electrostaticFoam source code appears to use the continuity equation (in bold), implying rho is not fixed in space:

Description
    Solver for electrostatics.

\*---------------------------------------------------------------------------*/

#include "fvCFD.H"

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

int main(int argc, char *argv[])
{
    #include "setRootCase.H"

    #include "createTime.H"
    #include "createMesh.H"
    #include "createFields.H"

    // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

    Info<< "\nStarting iteration loop\n" << endl;

    while (runTime.loop())
    {
        Info<< "Iteration = " << runTime.timeName() << nl << endl;

        solve
        (
            fvm::laplacian(phi) + rho/epsilon0
        );

        rhoFlux = -k*mesh.magSf()*fvc::snGrad(phi);

        solve
        (
            fvm::ddt(rho) + fvm::div(rhoFlux, rho)
        );

        runTime.write();

        Info<< "ExecutionTime = " << runTime.elapsedCpuTime() << " s"
            << "  ClockTime = " << runTime.elapsedClockTime() << " s"
            << nl << endl;
    }

    Info<< "End\n" << endl;

    return 0;
}

[cgerrity]

I was able to do this by copying and modying the electrostatics solver directly. The trick is to specify the charge density for every part of the mesh by looping through it and then running the solver. If you want fixed space charge, make sure your solver doesn't change rho.

[cjessup37]

Hi Cory,


I am new to C++ coding and OpenFOAM. What do you mean 'specifying the charge density for every part of the mesh by looping through it'? Could you possibly share your code?



For context, I am trying to use electrostaticFoam as a way to calculate the gravitational field (little g) of a mass(es). I have changed the epsilon constant to what it needs to be for gravity as well as the units of phi and rho. I am having trouble specifying rho. I still need to change the solver to include the little g calculation but that looks straightforward based on what I read in the OpenFoam user guide.


Thanks!
Cody