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Troubleshooting - Airfoil 2D case using simpleFoam

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Old   November 26, 2020, 23:57
Unhappy Troubleshooting - Airfoil 2D case using simpleFoam
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Juan Han NG
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Hi all,


I hope for some help to troubleshoot my simulation case. The results seem very weird where the residuals of pressure oscillates and the flow field in paraview looks unsteady (See attached figures).






The setup is listed below:
Turbulence Model: SpalartAllmaras
Re = 1e5
Airfoil: NACA4412



dynamic pressure

Quote:
boundaryField
{
inlet
{
type zeroGradient;
}
outlet
{
type fixedValue;
value uniform 0;
}
freestream
{
type fixedValue;
value uniform 0;
}
airfoil
{
type zeroGradient;
}
defaultFaces
{
type empty;
}
}

Velocity
Quote:
boundaryField
{
inlet
{
type fixedValue;
value uniform ( 1.46 0 0 );
}
outlet
{
type zeroGradient;
}
freestream
{
type fixedValue;
value uniform ( 1.46 0 0 );
}
airfoil
{
type noSlip;
value uniform ( 0 0 0 );
}
defaultFaces
{
type empty;
}
}

nut
Quote:
{
inlet
{
type freestream;
freestreamValue uniform 0;
value uniform 0;
}
outlet
{
type freestream;
freestreamValue uniform 0;
value uniform 0;
}
freestream
{
type freestream;
freestreamValue uniform 0;
value uniform 0;
}
airfoil
{
type nutUSpaldingWallFunction;
value uniform 0;
}
defaultFaces
{
type empty;
}
}

nuTilda
Quote:
{
inlet
{
type freestream;
freestreamValue uniform 1.46e-05;
value uniform 1.46e-05;
}
outlet
{
type freestream;
freestreamValue uniform 1.46e-05;
value uniform 1.46e-05;
}
freestream
{
type freestream;
freestreamValue uniform 1.46e-05;
value uniform 1.46e-05;
}
airfoil
{
type fixedValue;
value uniform 0;
}
defaultFaces
{
type empty;
}
}

checkMesh
Quote:
Checking geometry...
Overall domain bounding box ( -39.5912 -0.01 -40 ) ( 80 0.01 40 )
Overall domain volume 177.611
Mesh has 2 geometric (non-empty/wedge) directions ( 1 0 1 )
Mesh has 2 solution (non-empty) directions ( 1 0 1 )
All edges aligned with or perpendicular to non-empty directions.
Boundary openness ( 8.5522e-20 -1.35312e-15 -1.99324e-19 ) OK.
Max cell openness = 2.95391e-16 OK.
Max aspect ratio = 663.526 OK.
Minimum face area = 3.96081e-07. Maximum face area = 0.218572. Face area magnitudes OK.
Min volume = 7.92163e-09. Max volume = 0.00437143. Total volume = 177.611. Cell volumes OK.
Mesh non-orthogonality Max: 61.7016 average: 6.45041
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 0.923873 OK.
Coupled point location match (average 0) OK.

Mesh OK.

fvscheme
Quote:
ddtSchemes
{
default steadyState;
}

gradSchemes
{
default Gauss linear;
}

divSchemes
{
default Gauss linear;
div(phi,U) bounded Gauss linearUpwind grad(U);
div(phi,nuTilda) bounded Gauss linearUpwind grad(nuTilda);
div((nuEff*dev2(T(grad(U))))) Gauss linear;
}

laplacianSchemes
{
default Gauss linear corrected;
}

interpolationSchemes
{
default linear;
}

snGradSchemes
{
default corrected;
}

wallDist
{
method meshWave;
}

fvsolution
Quote:
solvers
{
p
{
solver GAMG;
tolerance 1e-06;
relTol 0.1;
smoother GaussSeidel;
agglomerator faceAreaPair;
mergeLevels 1;
cacheAgglomeration true;
nCellsInCoarsestLevel 200;
nPreSweeps 0;
nPostSweeps 2;
nFinestSweeps 2;
minIter 1;
}

U
{
solver smoothSolver;
smoother GaussSeidel;
nSweeps 2;
tolerance 1e-08;
relTol 0.1;
}

nuTilda
{
solver smoothSolver;
smoother GaussSeidel;
nSweeps 2;
tolerance 1e-08;
relTol 0.1;
}
}

SIMPLE
{
nNonOrthogonalCorrectors 0;
pRefCell 0;
pRefValue 0;

residualControl
{
p 1e-5;
U 1e-5;
nuTilda 1e-5;
}
}

relaxationFactors
{
fields
{
p 0.3;
}
equations
{
U 0.7;
nuTilda 0.7;
}
}

If anyone has any idea on the possible reason for this unsteady behavior of flow, please kindly comment here!
Attached Images
File Type: png Screenshot from 2020-11-27 12-44-20.png (8.3 KB, 9 views)
File Type: png Screenshot from 2020-11-27 12-55-14.png (72.5 KB, 10 views)
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Tags
airfoil 2d, naca4412, simple foam, spalart allmaras model, unsteady

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