[RjwV]

Hello everyone,

I believe I have found two errors in the Kinetic Theory of Granular Flow as implemented in OpenFOAM. I am currently working with v. 2.3.0, but counts for all versions up to 2.4.x.

Number one; the frictional pressure and viscosity have not been added to the solids pressure and solids shear viscosity before solving ThetaEqn. The code snippets as posted below here define nut and PsCoeff, which are directly used in ThetaEqn. In literature, usually the frictional pressure and viscosity are added before solving the granular energy equation.

nut_ = viscosityModel_->nu(alpha, Theta_, gs0_, rho, da, e_);

        volScalarField PsCoeff
        (
            granularPressureModel_->granularPressureCoeff
            (
                alpha,
                gs0_,
                rho,
                e_
            )
        );

Number two; In the Schaeffer frictional stress file, in the function for the viscosity, the frictional viscosity is only calculated if alpha1 exceeds alphaMax. In this case, alphaMax is the maximum packing of the solids, which should not be exceeded in any case, so the frictional viscosity should (theoretically) never be calculated in this case. I believe alphaMax should replaced be the minimum friction hold-up, alphaMinFriction.

        if (alpha1[celli] > alphaMax.value() - 5e-2)
        {
            nuf[celli] =
                0.5*pf[celli]*sin(phi_.value())
               /(
                    sqrt(1.0/6.0*(sqr(D[celli].xx() - D[celli].yy())
                  + sqr(D[celli].yy() - D[celli].zz())
                  + sqr(D[celli].zz() - D[celli].xx()))
                  + sqr(D[celli].xy()) + sqr(D[celli].xz())
                  + sqr(D[celli].yz())) + I2Dsmall
                );
        }

If anyone can comment on / confirm these possible errors, please let me know.

Kind regards,
Ramon

[ssss]

If you are sure of the bugs, you could send this bug report to the openfoam mantis, the developers will have a look at it

[wyldckat]

For future reference: http://www.openfoam.org/mantisbt/view.php?id=1831