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-   -   multiphaseEulerFoam - UEqn (http://www.cfd-online.com/Forums/openfoam/109606-multiphaseeulerfoam-ueqn.html)

mikeP November 21, 2012 13:52

multiphaseEulerFoam - UEqn
 
Hi,

I see that in mEF, the phase intensive formulation is not used.
Instead we have the UEqn as:
Code:

(scalar(1) + fluid.Cvm(phase)/phase.rho())*             
            (
                  fvm::ddt(alpha, U)
                + fvm::div(phase.phiAlpha(), U)
                - fvm::Sp(fvc::ddt(alpha) + fvc::div(phase.phiAlpha()), U)
              )
              - fvm::laplacian(alpha*nuEff, U)
              - fvc::div
                (
                    alpha*(nuEff*dev(T(fvc::grad(U))) /*- ((2.0/3.0)*I)*k*/),
                    "div(Rc)"
                )
            ==
              - fvm::Sp(fluid.dragCoeff(phase, dragCoeffs())/phase.rho(), U)
            //- (alpha*phase.rho())*fluid.lift(phase)
              + (alpha/phase.rho())*fluid.Svm(phase)

isn't there something wrong here?

1) why is the term ((2.0/3.0)*I)*k) commented out?

2) shouldn't it be
alpha*(nuEff*dev(symm(fvc::grad(U))) /*- ((2.0/3.0)*I)*k*/),
instead of
alpha*(nuEff*dev(T(fvc::grad(U))) /*- ((2.0/3.0)*I)*k*/),

Thanks

mikeP November 22, 2012 18:39

isn't this part:

Code:

- fvm::laplacian(alpha*nuEff, U)
              - fvc::div               
                (
                    alpha*(nuEff*dev(T(fvc::grad(U))) /*- ((2.0/3.0)*I)*k*/),
                    "div(Rc)"
                )

should be like this?

Code:

- fvc::div
                (
                    alpha*(nuEff*2*dev(symm(fvc::grad(U))) - ((2.0/3.0)*I)*k),
                    "div(Rc)"
                )


kwardle November 26, 2012 12:40

I can check into this, but I think the answer is that mEF was written with LES only in mind and is not set up for RAS turbulence at all.
-Kent

yanxiang December 18, 2012 15:25

hmm... This is weird. It this OF210 you are using? In OF211, it is formulated as follows:

Code:

    UEqns.set
    (
        phasei,
        new fvVectorMatrix
        (
            fvm::ddt(alpha, U)
          + fvm::div(phase.phiAlpha(), U)
          - fvm::Sp(fvc::ddt(alpha) + fvc::div(phase.phiAlpha()), U)

          + (alpha/phase.rho())*fluid.Cvm(phase)*
            (
                fvm::ddt(U)
              + fvm::div(phase.phi(), U)
              - fvm::Sp(fvc::div(phase.phi()), U)
            )

          - fvm::laplacian(alpha*nuEff, U)
          - fvc::div
            (
                alpha*(nuEff*dev(T(fvc::grad(U))) /*- ((2.0/3.0)*I)*k*/),
                "div(Rc)"
            )
        ==
          - fvm::Sp(fluid.dragCoeff(phase, dragCoeffs())/phase.rho(), U)
        //- (alpha*phase.rho())*fluid.lift(phase)
          + (alpha/phase.rho())*fluid.Svm(phase)
          - fvm::Sp
            (
                slamDampCoeff
              *max
                (
                    mag(U.dimensionedInternalField()) - maxSlamVelocity,
                    dimensionedScalar("U0", dimVelocity, 0)
                )
              /pow(mesh.V(), 1.0/3.0),
                U
            )
        )
    );

It seemed the first term has been split into two parts. Do you have any idea what the difference is between phase.phiAlpha() and phase.phi()?

Thanks,
Yanxiang

mikeP March 22, 2013 06:34

I am bumping up this thread, but there is something strange with twoPhaseEulerFoam when I compare its code in OF2.0, OF2.1, and OF2.2

In OF2.0, there is the term with the turbulent kinetic energy in the definition of the reynolds stresses, as it should.
see line 21 in (https://github.com/OpenFOAM/OpenFOAM...erFoam/UEqns.H)

But this term is vanished in 2.1 and 2.2.
see line 21 in (https://github.com/OpenFOAM/OpenFOAM...erFoam/UEqns.H)

why is that?


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