[bumi-the-man]

Hi guys,

I'm struggling a bit with the following problem:

I want so simulate a simple pipe flow with particles (straitght pipe with inlet and outlet). The bulk fluid is water-like, Newtonian liquid whereas the particles are alginate particles with a density close to the one of water and a average diameter of 900um. I manage to solve the case with the MPPICFoam solver, however, the pressure always acts super weird. There are strange pressure fluctuations and unphysical sudden changes in the kinematic pressure. Also, the pressure does not converge during solving. The velocity field looks plausible.

I tried to adapt the fvSchemes and fvSolution files, but nothing really resolves the problem. I took the fvSchemes and fvSolution from existing cases for incompressible, lagrangian particle-flow problems where all use air as their continuous medium - this might be the issue since in my case, the continuous phase is much denser and more viscous. I change from GAMG to PCG solver for pressure and increased the convergence criteria. But it didn't change anything

I also tried to solved only the flow field of the bulk phase without particle using MPPICFoam, and there, the pressure looked good. So as soon as particles are introduced, the pressure starts to act weird...

I also played around with the boundary conditions. Do you have an suggestion for a suitable setup of fvSchemes and fvSolutions?


fvSchemes

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2212                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      fvSchemes;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

ddtSchemes
{
    default         Euler;
}

d2dt2Schemes
{
    default         Euler;
}

gradSchemes
{
    default         Gauss linear;
}

divSchemes
{
    default         none;

    div(alphaPhi.cont,U.cont)    Gauss linearUpwindV unlimited;
    div(((alpha.cont*nuEff.cont)*dev2(T(grad(U.cont))))) Gauss linear;

    div(phiGByA,kinematicCloud:alpha) Gauss linear;
}

laplacianSchemes
{
    default         Gauss linear corrected;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         corrected;
}


// ************************************************************************* //

fvSolution

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2212                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

solvers
{
    p
    {
        solver          PCG;
        preconditioner  DIC;
        tolerance       1e-10;
        relTol          0;
    };

    pFinal
    {
        $p;
        relTol          0;
    }

    pcorrFinal
    {
        $p;
        relTol          0;
    }

    U.cont
    {
        solver          smoothSolver;
        smoother        symGaussSeidel;
        tolerance       1e-05;
        relTol          0.1;
    }

    U.contFinal
    {
        solver          smoothSolver;
        smoother        symGaussSeidel;
        tolerance       1e-05;
        relTol          0;
    }

    kinematicCloud:alpha
    {
        solver          smoothSolver;
        smoother        symGaussSeidel;
        tolerance       1e-06;
        relTol          0;
    }
}

PIMPLE
{
    nOuterCorrectors 1;
    nCorrectors     2;
    momentumPredictor yes;
    nNonOrthogonalCorrectors 0;
    pRefCell        0;
    pRefValue       0;
    checkMeshCourantNo  no;
    correctPhi          no;
}

relaxationFactors
{
    fields
    {
        ".*"            1;
    }
    equations
    {
        ".*"            1;
    }
}


// ************************************************************************* //

0/p

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2212                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    object      p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 2 -2 0 0 0 0];

internalField   uniform 0;

boundaryField
{
	inlet1
	{
   		 type            zeroGradient;
	}

  	outlet
   	 {
    	    type            fixedValue;
    	    value           uniform 0;
   	 }

    walls
    {
        type            zeroGradient;
    }
}


// ************************************************************************* //

0/U.cont

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2212                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volVectorField;
    object      U.cont;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 1 -1 0 0 0 0];

internalField   uniform (0 0 0);

boundaryField
{
	inlet1
	{
 	type            fixedValue;
	value           uniform (0.3 0 0);
	}

 outlet
    {
        type            zeroGradient;
	value           uniform (0 0 0);
    }


    walls
    {
        type            noSlip;
    }
}


// ************************************************************************* //