[Algis]

Hi,

Why for some cases pEqn().flux() are subtracted, as for example:

phi = phiHbyA - pEqn().flux()

as in applications\solvers\incompressible\simpleFoam\pEq n.H,

while for other cases are added, as for example

phi = phiHbyA + pEqn().flux()

as in applications\solvers\compressible\rhoSimpleFoam\pE qn.H?

Thanks in advance,

[hjasak]

If your pressure laplacian has a minus sign (-), then it's

phi = phiHbyA + pEqn().flux()

This is the case in compressible solvers.

For incompressible solvers, the pressure laplacian has a positive sign and it's

phi = phiHbyA - pEqn().flux()

Hrv

[Algis]

Thank you very much.

[rapierrz]

Hi,

what is flux() function in phi -= pEqn.flux() ?

thank u.

[cfdopenfoam]

Originally Posted by hjasak

If your pressure laplacian has a minus sign (-), then it's

phi = phiHbyA + pEqn().flux()

This is the case in compressible solvers.

For incompressible solvers, the pressure laplacian has a positive sign and it's

phi = phiHbyA - pEqn().flux()

Hrv

hello Dr. jasak.

i wonder if the + or - operation depends on how the pEqn is declared.

i mean for the incompressible solver pimpleFoam, the pEqn is

    fvScalarMatrix pEqn
    (
        fvm::laplacian(rAUf, p) == fvc::div(phiHbyA)
    );

thus the conservative face fluxes are constructed as

phi = phiHbyA - pEqn.flux();

then if i change the pEqn like

    fvScalarMatrix pEqn
    (
        fvm::laplacian(rAUf, p) - fvc::div(phiHbyA)
    );

or

    fvScalarMatrix pEqn
    (
        - fvm::laplacian(rAUf, p) + fvc::div(phiHbyA)
    );

then how the flux phi will be corrected to ensure conservative?

another question, for the shallowWaterFoam, the "pEqn" is

fvScalarMatrix hEqn
                    (
                        fvm::ddt(h)
                      + fvc::div(phiHbyA)
                      - fvm::laplacian(ghrAUf, h)
                    );

with a temporal derivative, so how the hEqn.flux() will be calculated? and why the flux phi is corrected by

phi = phiHbyA + hEqn.flux();

the last question also post here.

thanks very much for your valuable time.

best,

karelke