[Jh97]

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

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

Velocity

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

{
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

{
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

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

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

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!