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Using rhoSimpleFoam for simulating steady state flow in a CD nozzle

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Old   January 14, 2020, 07:14
Default Using rhoSimpleFoam for simulating steady state flow in a CD nozzle
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Vignesh
Join Date: Nov 2019
Location: Dresden, Germany
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Hello everyone,


I'm trying to simulate a steady state CFD simulation in a CD nozzle using the solver rhoSimpleFoam. I'm facing some issues and I'm not able to validate my results.

I have attached all my files below.


I've created a very simple mesh in blockMesh, and have introduced mesh grading to refine the areas near the boundary. I attach my checkMesh results below

Code:

Build  : v1906 OPENFOAM=1906
Arch   : "LSB;label=32;scalar=64"
Exec   : checkMesh

Create time

Create mesh for time = 0

Time = 0

Mesh stats
    points:           121402
    internal points:  0
    faces:            240700
    internal faces:   119300
    cells:            60000
    faces per cell:   6
    boundary patches: 5
    point zones:      0
    face zones:       0
    cell zones:       0

Overall number of cells of each type:
    hexahedra:     60000
    prisms:        0
    wedges:        0
    pyramids:      0
    tet wedges:    0
    tetrahedra:    0
    polyhedra:     0

Checking topology...
    Boundary definition OK.
    Cell to face addressing OK.
    Point usage OK.
    Upper triangular ordering OK.
    Face vertices OK.
    Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
    Patch               Faces    Points   Surface topology                  
    inlet               100      202      ok (non-closed singly connected)  
    outlet              100      202      ok (non-closed singly connected)  
    upperWall           600      1202     ok (non-closed singly connected)  
    lowerWall           600      1202     ok (non-closed singly connected)  
    frontAndBack        120000   121402   ok (non-closed singly connected)  

Checking faceZone topology for multiply connected surfaces...
    No faceZones found.

Checking basic cellZone addressing...
    No cellZones found.

Checking geometry...
    Overall domain bounding box (0 0 -0.0005) (0.007 0.00065 0.0005)
    Mesh has 2 geometric (non-empty/wedge) directions (1 1 0)
    Mesh has 2 solution (non-empty) directions (1 1 0)
    All edges aligned with or perpendicular to non-empty directions.
    Boundary openness (-9.4603783e-18 -2.5693272e-15 -9.6253206e-16) OK.
    Max cell openness = 3.1682644e-16 OK.
    Max aspect ratio = 4.1564656 OK.
    Minimum face area = 2.6926964e-11. Maximum face area = 1.1995734e-08.  Face area magnitudes OK.
    Min volume = 2.6926964e-14. Max volume = 1.3989641e-13.  Total volume = 4.025e-09.  Cell volumes OK.
    Mesh non-orthogonality Max: 2.4483775 average: 1.6573628
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 0.1068957 OK.
    Coupled point location match (average 0) OK.

Mesh OK.

End

For my boundary conditions, I specify that it is a pressure driven flow, with totalPressure BC at the inlet and fixedValue at the outlet.
For velocity, I specify zeroGradient at both inlet and outlet, with noSlip at the top wall
For temperature, I specify fixedValue at the inlet and zeroGradient at the outlet.
I also use symmetryPlane BC for the lower wall.


I have attached my boundary conditions below.


Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v1906                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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


internalField   uniform 101325;

boundaryField
{
    inlet
    {
        type            totalPressure;
        p0              uniform 200000;
        U               U;
        phi             phi;
        rho             rho;
        psi             none;
        gamma           1.4;   
    }
    outlet
    {
        type            fixedValue;
        value           uniform 101325;
        U               U;
        phi             phi;
        rho             rho;
        psi             none;
        gamma           1.4;
    }
    upperWall
    {
        type            zeroGradient;
    }
    lowerWall
    {
        type            symmetryPlane;
    }
    frontAndBack
    {
        type            empty;
    }
    defaultFaces
    {
    type         empty;
    }
}

Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v1906                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volVectorField;
    location    "0";
    object      U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform (0 0 0);

boundaryField
{
    inlet
    {
        type            zeroGradient;
    }
    outlet
    {
        type            zeroGradient;
    }
    upperWall
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    lowerWall
    {
        type            symmetryPlane;
    }
    frontAndBack
    {
        type            empty;
    }
}

Code:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v1906                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      T;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 0 0 1 0 0 0];


internalField   uniform 298;

boundaryField
{
    inlet
    {
        type            totalTemperature;
        T0              uniform 298;
        gamma           1.4;
    }
    outlet
    {
        type            zeroGradient;
    }
    upperWall
    {
        type            zeroGradient;
    }
    lowerWall
    {
        type            symmetryPlane;
    }
    frontAndBack
    {
        type            empty;
    }
}

I have read many posts in this forum, and people have recommended using the above boundary conditions for this case, so I'm not sure if there is a problem with this.


I'm attaching my fvSchemes, fvOptions and fvSolution files below. I'm not particularly sure as to which solver to use for this case, so I've just gone with the ones used in the tutorials.


Code:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v1906                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      fvSchemes;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

ddtSchemes
{
    default         steadyState;
}

gradSchemes
{
    default         Gauss linear;
}

divSchemes
{
    default             none;

    div(phi,U)          bounded Gauss upwind;
    div(((rho*nuEff)*dev2(T(grad(U)))))      Gauss linear;
    div(phi,e)          bounded Gauss upwind;
    div(phi,epsilon)    bounded Gauss upwind;
    div(phi,k)          bounded Gauss upwind;

    div(phid,p)         Gauss upwind;
    div(phi,Ekp)        bounded Gauss upwind;
    div((phi|interpolate(rho)),p)  Gauss upwind;
}

laplacianSchemes
{
    default         Gauss linear corrected;
}

interpolationSchemes
{
    default         linear;
}

gradSchemes
{
    default         faceMDLimited Gauss linear 0.5;
}

Code:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v1906                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

solvers
{
    p
    {
        solver          GAMG;
        smoother        GaussSeidel;
        tolerance       1e-6;
        relTol          0.01;
    }

    "(U|k|omega|e)"
    {
        solver          PBiCGStab;
        preconditioner  DILU;
        tolerance       1e-6;
        relTol          0.01;
    }
}

SIMPLE
{
    residualControl
    {
        p               1e-4;
        U               1e-4;
        "(k|omega|e)"   1e-4;
    }

    nNonOrthogonalCorrectors 0;
    pMinFactor      0.1;
    pMaxFactor      2;
}

relaxationFactors
{
    fields
    {
        p               0.7;
        rho             0.01;
    }
    equations
    {
        U               0.3;
        e               0.7;
        "(k|omega)"     0.7;
    }
}

Code:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v1906                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      fvOptions;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

limitT
{
    type       limitTemperature;
    min        101;
    max        1000;
    selectionMode all;
}

I'm getting some pretty weird results, and I'm not able to validate my pressure and velocity plots with the literature.

Code:

# Solver information
# Time              U_solver            Ux_initial          Ux_final            Ux_iters            Uy_initial          Uy_final            Uy_iters            U_converged         p_solver            p_initial           p_final             p_iters             p_converged     
1                   DILUPBiCGStab    1.00000000e+00    5.63145200e-03    1    1.00000000e+00    1.18017460e-03    1    false    GAMG    1.00000000e+00    3.08416040e-03    1    true
2                   DILUPBiCGStab    5.45963700e-01    1.69905430e-03    1    3.80739180e-01    1.41675240e-03    1    false    GAMG    2.26367420e-01    1.35376850e-03    3    true
3                   DILUPBiCGStab    4.30959060e-01    1.18852260e-03    1    2.92858160e-01    9.58617740e-04    1    false    GAMG    5.43492460e-02    3.31423630e-04    5    true
4                   DILUPBiCGStab    3.20779760e-01    8.65311860e-04    1    3.13826670e-01    9.23813840e-04    1    false    GAMG    1.69414160e-02    1.34136910e-04    5    true
5                   DILUPBiCGStab    2.56209780e-01    6.71257920e-04    1    1.71144620e-01    1.22977570e-03    1    false    GAMG    1.21129840e-02    1.03227820e-04    7    true
6                   DILUPBiCGStab    2.17978780e-01    6.08204110e-04    1    9.04764450e-02    7.59603610e-04    1    false    GAMG    6.80493660e-03    3.89629250e-05    9    true
7                   DILUPBiCGStab    1.88510680e-01    5.48296570e-04    1    5.44852170e-02    5.07802030e-04    1    false    GAMG    3.11672060e-03    1.45205410e-05    8    true
8                   DILUPBiCGStab    1.65910160e-01    5.03121960e-04    1    5.41494690e-02    2.58120990e-04    1    false    GAMG    1.78527080e-03    1.27787290e-05    10    true
9                   DILUPBiCGStab    1.48527580e-01    4.63248670e-04    1    5.09946720e-02    1.67642980e-04    1    false    GAMG    1.64403040e-03    1.33992420e-05    7    true
10                  DILUPBiCGStab    1.35567040e-01    4.37185820e-04    1    4.29566890e-02    1.33335920e-04    1    false    GAMG    1.14007820e-03    5.09410220e-06    9    true
11                  DILUPBiCGStab    1.25101200e-01    4.15358040e-04    1    3.67467390e-02    1.16270810e-04    1    false    GAMG    6.55856160e-04    5.55730280e-06    10    true
12                  DILUPBiCGStab    1.16331370e-01    3.94785310e-04    1    3.33904360e-02    1.14179040e-04    1    false    GAMG    4.08227720e-04    2.61137050e-06    10    true
13                  DILUPBiCGStab    1.08920730e-01    3.77537340e-04    1    3.04151770e-02    1.00107160e-04    1    false    GAMG    3.19891450e-04    1.40731650e-06    10    true
14                  DILUPBiCGStab    1.02434070e-01    3.60374460e-04    1    2.76140780e-02    8.70842780e-05    1    false    GAMG    3.38320430e-04    2.80018250e-06    8    true
15                  DILUPBiCGStab    9.68027690e-02    3.45042220e-04    1    2.51560640e-02    7.97026030e-05    1    false    GAMG    2.95921630e-04    2.04757530e-06    10    true
16                  DILUPBiCGStab    9.18175200e-02    3.30619640e-04    1    2.31945540e-02    7.53207720e-05    1    false    GAMG    2.78887010e-04    2.13555550e-06    10    true
17                  DILUPBiCGStab    8.73560160e-02    3.17040200e-04    1    2.14896960e-02    7.10223110e-05    1    false    GAMG    2.61539370e-04    1.78062630e-06    10    true
18                  DILUPBiCGStab    8.33385690e-02    3.04377940e-04    1    2.00176410e-02    6.69856460e-05    1    false    GAMG    2.39387170e-04    1.52502490e-06    10    true
19                  DILUPBiCGStab    7.96829250e-02    2.92397810e-04    1    1.87329790e-02    6.35358290e-05    1    false    GAMG    2.24885040e-04    1.49790800e-06    10    true
20                  DILUPBiCGStab    7.63413040e-02    2.81126890e-04    1    1.75887980e-02    6.02910410e-05    1    false    GAMG    2.10218520e-04    1.53493880e-06    10    true
21                  DILUPBiCGStab    7.32650410e-02    2.70438530e-04    1    1.65726370e-02    5.73083060e-05    1    false    GAMG    1.91872990e-04    1.52267420e-06    10    true
22                  DILUPBiCGStab    7.04232370e-02    2.60365690e-04    1    1.56758180e-02    5.46103790e-05    1    false    GAMG    1.81844850e-04    1.50381060e-06    10    true
23                  DILUPBiCGStab    6.77782630e-02    2.50757110e-04    1    1.48653250e-02    5.21972350e-05    1    false    GAMG    1.72173430e-04    1.45175550e-06    10    true
24                  DILUPBiCGStab    6.53140050e-02    2.41670020e-04    1    1.41437450e-02    4.99757360e-05    1    false    GAMG    1.73370400e-04    1.46278090e-06    10    true
25                  DILUPBiCGStab    6.30025590e-02    2.32989500e-04    1    1.34863160e-02    4.79381780e-05    1    false    GAMG    1.71632110e-04    1.44063250e-06    10    true
26                  DILUPBiCGStab    6.08374200e-02    2.24776930e-04    1    1.28970280e-02    4.60580520e-05    1    false    GAMG    1.79620720e-04    1.48070940e-06    10    true
27                  DILUPBiCGStab    5.87925880e-02    2.16906900e-04    1    1.23541050e-02    4.43544230e-05    1    false    GAMG    1.78122980e-04    1.47343430e-06    10    true
28                  DILUPBiCGStab    5.68701380e-02    2.09467830e-04    1    1.18693010e-02    4.27715320e-05    1    false    GAMG    1.92241980e-04    1.55318520e-06    10    true
29                  DILUPBiCGStab    5.50387110e-02    2.02284800e-04    1    1.14108410e-02    4.13368420e-05    1    false    GAMG    1.83502800e-04    1.52036720e-06    10    true
30                  DILUPBiCGStab    5.33225160e-02    1.95563590e-04    1    1.10138510e-02    3.99818580e-05    1    false    GAMG    2.19881880e-04    1.69307790e-06    10    true
31                  DILUPBiCGStab    5.16611490e-02    1.88944310e-04    1    1.06115980e-02    3.87271670e-05    1    false    GAMG    1.94226080e-04    1.05166710e-06    9    true
32                  DILUPBiCGStab    5.01307010e-02    1.82932710e-04    1    1.03014500e-02    3.75655170e-05    1    false    GAMG    2.83234270e-04    2.64408350e-06    9    true
33                  DILUPBiCGStab    4.85968080e-02    1.76766330e-04    1    9.92182590e-03    3.64379860e-05    1    false    GAMG    2.07138410e-04    1.01193740e-06    11    true
34                  DILUPBiCGStab    4.72464770e-02    1.71468870e-04    1    9.69155610e-03    3.55057620e-05    1    false    GAMG    3.93283910e-04    3.05400540e-06    9    true
35                  DILUPBiCGStab    4.58148180e-02    1.65662860e-04    1    9.31109310e-03    3.43954260e-05    1    false    GAMG    2.28560780e-04    1.92363650e-06    11    true
36                  DILUPBiCGStab    4.45977370e-02    1.60842140e-04    1    9.16470370e-03    3.39266820e-05    1    false    GAMG    4.28370440e-04    3.43084120e-06    9    true
37                  DILUPBiCGStab    4.32852850e-02    1.55414630e-04    1    8.82190370e-03    3.25834400e-05    1    false    GAMG    2.43366240e-04    1.66772150e-06    11    true
38                  DILUPBiCGStab    4.21815780e-02    1.51078060e-04    1    8.64352460e-03    3.19734930e-05    1    false    GAMG    4.77693940e-04    3.41435100e-06    9    true
39                  DILUPBiCGStab    4.09662000e-02    1.46093860e-04    1    8.34459010e-03    3.09677080e-05    1    false    GAMG    2.72134740e-04    2.10972370e-06    11    true
40                  DILUPBiCGStab    3.99430810e-02    1.42052270e-04    1    8.22838910e-03    3.06635910e-05    1    false    GAMG    4.75725740e-04    3.50940940e-06    9    true

I've attached my residuals log for the first 40 iterations. I notice that U_converged is always false, all the way, while p_converged is showing true.

I don't know if it's a problem with my boundary conditions, mesh or system properties. I've been breaking my head with this for a while. Can someone please help me out? I'd really appreciate it.
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