[shereez234]

I have read a lot of posts in this forum regarding Wall Functions in OF. But could not arrive at an answer that satisfies me.

I have a mesh for Naca 0012 airfoil with Y+ ~= 1

My understanding up to now:

1) Without Wall function - ( wall/airfoil/solidwall) (// Y+ less than or =1)
* Omega -
Type: omegaWallfunction
value: 1e-18; // non zero low value

* K
Type: KqRWallfunction
value: 1e-18 ; // non zero low value

* nut Type : nutkWallfunction
value: uniform 0;


2) With Wall function - ( wall/airfoil/solidwall) (Y+ 30 to 100)
* Omega
Type: omegaWallfunction
value: 300; // some value from formulaes or guess

* K Type: KqRWallfunction
value: 0.1 ; // some value

* nut Type: KqRWallfunction
value: uniform 0;

Is this correct? Or what is the actual implementation: I intend to use without wall functions.

Some other information that might be useful:

* Re = 2 million
* Mach = incompressible
* K = turbulentKineticEnergyinlet with intensity specified
* High Angle of Attack region.

* FV schemes:
(divergence of U)
* bounded Gauss limitedLinearV 1;

(divergence of k|Omega)
*bounded Gauss limitedLinear 1;

* Time Integration: Euler

please input your views. Any input is appreciated very much

[jherb]

For the case with Y+=1 have a look in this thread:

http://www.cfd-online.com/Forums/ope...estigated.html

For k fixedValue is suggested and for nut calculated (so no wall functions).

[shereez234]

First, my apologies. I should have seen this thread you guided me to.

And This reference seems very helpful. Thanks a lot. Will investigate further into this.

[shereez234]

Right Okay. So I gave this a try and suprisingly: it did not seem to work well. I have changed fv schemes around a lot. I am getting bounding omega to be jumping from 1 to a really high value ( 1e58 or may be more) and solution stops.

After reading the post you reffered me to:

1) I have mesh for Naca0012 with size = 24,000 elements - hexa - quads.
This mesh converges in fluent.

Turbulent intensity = 0.05 % and laminar to turbulent ( eddy visc ratio = 0.009) giving me a Omega Wall ( Menter's propsition) = 1.9e08 at the wall(airfoil in this case).

Here is my file details:

k
boundaryField
{
CRVS
{
type fixedValue;
value uniform 1e-18;
}
INLET
{
type turbulentIntensityKineticEnergyInlet;
intensity 0.052;
value uniform 0.219;

omega
CRVS
{
type fixedValue;
value uniform 1.9e+008;
Cmu 0.09;
kappa 0.41;
E 9.8;
beta1 0.075;
}
INLET
{
type inletOutlet;
inletValue uniform 0;
value uniform 0;

Solver: PISOFOAM
deltaT 0.000000002;

fvschemes
ddtSchemes
{
default backward;
}

gradSchemes
{
default leastSquares;
grad(p) Gauss linear;
grad(U) Gauss linear;
}

divSchemes
{
default none;
div(phi,U) bounded Gauss upwind;
div(phi,k) bounded Gauss upwind;
div(phi,omega) bounded Gauss upwind;
div((nuEff*dev(T(grad(U))))) Gauss linear;
}

laplacianSchemes
{
default Gauss linear corrected;
}

interpolationSchemes
{
default linear;
}

snGradSchemes
{
default corrected;
}

fluxRequired
{
default no;
p ;
Phi ;

}
fvSolution
solvers
{
p
{
solver GAMG;
tolerance 1e-07;
relTol 0.1;
smoother GaussSeidel;
cacheAgglomeration true;
nCellsInCoarsestLevel 10;
agglomerator faceAreaPair;
mergeLevels 1;
maxIter 1000;
}

pFinal
{
solver GAMG;
tolerance 1e-6;
relTol 0;
smoother GaussSeidel;
}

Phi
{
$p;
}

U
{
solver smoothSolver;
smoother GaussSeidel;
nSweeps 1;
tolerance 1e-08;
relTol 0.1;
maxIter 1000;
}
k
{
solver smoothSolver;
smoother GaussSeidel;
tolerance 1e-8;
relTol 0.1;
nSweeps 1;
maxIter 1000;
}

omega
{
solver smoothSolver;
smoother GaussSeidel;
tolerance 1e-8;
relTol 0.1;
nSweeps 1;
maxIter 1000;
}
}

PISO
{
nCorrectors 2;
nNonOrthogonalCorrectors 0;
pRefCell 0;
pRefValue 0;

residualControl
{
p 1e-5;
U 1e-5;
}
}
potentialFlow
{
nNonOrthogonalCorrectors 10;
pRefCell 0;
pRefValue 0;
PhiRefCell 0;
PhiRefPoint 0;
PhiRefValue 0;
Phi 0;
}
relaxationFactors
{
fields
{
p 0.1;
}
equations
{
U 0.1;
omega 0.1;
k 0.1;
}
}


Error Message:
Time = 1.8e-008

Courant Number mean: 6.6089e+010 max: 5.96403e+018
smoothSolver: Solving for Ux, Initial residual = 0.0854157, Final residual = 0.00162756, No Iterations 2
smoothSolver: Solving for Uy, Initial residual = 0.0857431, Final residual = 0.0083747, No Iterations 1
GAMG: Solving for p, Initial residual = 0.840767, Final residual = 0.0795824, No Iterations 2
time step continuity errors : sum local = 6.50813e+016, global = 1.35752, cumulative = 1.35752
GAMG: Solving for p, Initial residual = 0.996139, Final residual = 8.94264e-007, No Iterations 40
time step continuity errors : sum local = 2.66843e+022, global = 1.26249e+007, cumulative = 1.26249e+007
smoothSolver: Solving for omega, Initial residual = 0.999561, Final residual = 0.0112157, No Iterations 4
bounding omega, min: 0 max: 1.39292e+063 average: 7.77122e+058
smoothSolver: Solving for k, Initial residual = 0.363297, Final residual = 3.7894e-019, No Iterations 1
bounding k, min: 1e-018 max: 33.6809 average: 0.36149
ExecutionTime = 26.234 s ClockTime = 26 s


Regards and thanks in advance for any one willing to share ideas and experience.

[akidess]

Did you carefully read the thread Joachim linked? If so, I'm surprised by your choice of boundary conditions. By the way, please use "[code]" tags to make your post more readable.