[Carlen]

Hi Foamers,

I intend to realise a semi-implicit fractional step in OpenFOAM but got stuck at the final step where the flux phi is updated. Please see the code here:

// Create Poisson Matrix
    fvScalarMatrix pEqn
    (
        fvm::laplacian(p)
    );
    pEqn.setReference(pRefCell, pRefValue);

// PressureCorrection.H 
    solve(pEqn==fvc::div(U)/runTime.deltaT());
    phi -= pEqn.flux();// This is where I have problem.
    U -= runTime.deltaT()*fvc::grad(p);
    U.correctBoundaryConditions();

According to Jasak, if there is a plus sign before laplacian (p) then it should be:

    phi -= pEqn.flux();

otherwise it should be

    phi += pEqn.flux();

However, I cannot get very good mass conservation from both of them. Or there are other ways to update flux? PS: I am solving momentum equation implicitly using second order backward.

Thanks for your help,

Carlen

[gu1]

Originally Posted by Carlen

Hi Foamers,

I intend to realise a semi-implicit fractional step in OpenFOAM but got stuck at the final step where the flux phi is updated. Please see the code here:

// Create Poisson Matrix
    fvScalarMatrix pEqn
    (
        fvm::laplacian(p)
    );
    pEqn.setReference(pRefCell, pRefValue);

// PressureCorrection.H 
    solve(pEqn==fvc::div(U)/runTime.deltaT());
    phi -= pEqn.flux();// This is where I have problem.
    U -= runTime.deltaT()*fvc::grad(p);
    U.correctBoundaryConditions();

According to Jasak, if there is a plus sign before laplacian (p) then it should be:

    phi -= pEqn.flux();

otherwise it should be

    phi += pEqn.flux();

However, I cannot get very good mass conservation from both of them. Or there are other ways to update flux? PS: I am solving momentum equation implicitly using second order backward.

Thanks for your help,

Carlen

Did you solve this problem?