[dld]

Hello,


i want to simulate the flow of helium between two gas reservoirs through a microscopic channel (d = 60 um).


On one side I pump in with a pressure of 100 bar, the other side is evacuated using a vacuum pump. Both sides are connected by a small channel (d = 60um, l = 2mm). I attached a sketch of the setup. For now I set the pressure in the low pressure region to 1 bar. In the end I'm interested in the pressure distribution and the mass flow rate.



I managed to achieve some results by using setFields. I set the pressures in the high pressure region to 100 bar and to 1 bar every else. Afterwards I could see how it evolved over time. (I copied the decompressionTank tutorial and used rhoPimpleFoam)


To save time, I just wanted to simulate the pressure driven flow in a circular pipe using rhoPimpleFoam.



I set the folliwng boundary conditions for p and U. I tried to estimate the flow velocity and set it as internalField.

/*--------------------------------*- C++ -*----------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  7
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [1 -1 -2 0 0 0 0]; // Pascal

internalField   uniform 1e5;

boundaryField
{
    axis
    {
        type            empty;
    }
    inlet
    {
        type            totalPressure;
        p0              uniform 1e7;
        value           $internalField;
        
    }
    wall
    {
        type            zeroGradient;
    }
    outlet
    {
        type            fixedValue;
        value           uniform 1e5;
    }
    front
    {
        type            wedge;
    }
    back
    {
        type            wedge;
    }
}


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

/*--------------------------------*- C++ -*----------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  7
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volVectorField;
    location    "0";
    object      U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform (800 0 0);

boundaryField
{
    axis
    {
        type            empty;
    }
    inlet
    {
        type            zeroGradient;
    }
    wall
    {
        type            noSlip;
    }
    outlet
    {
        type            zeroGradient;
    }
    front
    {
        type            wedge;
    }
    back
    {
        type            wedge;
    }
}


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

For helium I set the following thermophysicalProperties

/*--------------------------------*- C++ -*----------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  7
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "constant";
    object      thermophysicalProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

thermoType
{
    type            heRhoThermo;
    mixture         pureMixture;
    transport       const;
    thermo          hConst;
    equationOfState perfectGas;
    specie          specie;
    energy          sensibleInternalEnergy;
}

mixture
{
    specie
    {
        nMoles          1;
        molWeight       4;
    }
    thermodynamics
    {
        Cp              5193.2;
        Hf              0;
    }
    transport
    {
        mu              1.96e-5;
        Pr              0.424;
    }
}

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

I tried around a lot, but when I try to run the simulation I always get an error like this:

#0  Foam::error::printStack(Foam::Ostream&) at ??:?
#1  Foam::sigFpe::sigHandler(int) at ??:?
#2  ? in "/usr/lib/libc.so.6"
#3  Foam::symGaussSeidelSmoother::smooth(Foam::word const&, Foam::Field<double>&, Foam::lduMatrix const&, Foam::Field<double> const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&, unsigned char, int) at ??:?
#4  Foam::symGaussSeidelSmoother::smooth(Foam::Field<double>&, Foam::Field<double> const&, unsigned char, int) const at ??:?
#5  Foam::smoothSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#6  ? in "/opt/OpenFOAM/OpenFOAM-7/platforms/linux64GccDPInt32Opt/bin/rhoPimpleFoam"
#7  ? in "/opt/OpenFOAM/OpenFOAM-7/platforms/linux64GccDPInt32Opt/bin/rhoPimpleFoam"
#8  ? in "/opt/OpenFOAM/OpenFOAM-7/platforms/linux64GccDPInt32Opt/bin/rhoPimpleFoam"
#9  ? in "/opt/OpenFOAM/OpenFOAM-7/platforms/linux64GccDPInt32Opt/bin/rhoPimpleFoam"
#10  __libc_start_main in "/usr/lib/libc.so.6"
#11  ? in "/opt/OpenFOAM/OpenFOAM-7/platforms/linux64GccDPInt32Opt/bin/rhoPimpleFoam"
Floating point exception (core dumped)

I'm quite new to CFD simulation, could you give me some pointers in the right direction? I also attached the whole case directory.

[Sakun]

Hi,


i do have the exactly the same boundary conditions and error for my compressor blade simulation and did you able to find the solution ?