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multiphaseEulerFoam - UEqn

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Old   November 21, 2012, 13:52
Default multiphaseEulerFoam - UEqn
  #1
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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
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Old   November 22, 2012, 18:39
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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)" 
                )
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Old   November 26, 2012, 12:40
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Kent Wardle
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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
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Old   December 18, 2012, 15:25
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Yanxiang Shi
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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
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Old   March 22, 2013, 06:34
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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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