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2nd Order Convergence Problem for 3D Airfoil

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Old   September 8, 2015, 09:16
Unhappy 2nd Order Convergence Problem for 3D Airfoil
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Gokce Turkmen
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Hi everyone,

I am working on simulating flow over 3D airfoil. I solved my case in first order Simplefoam but now I want to solve it in second order. But I didnt verify my first order result, it seemed good to me.

I tried different schemes only one of it converged but the residuals were higher than my first order. I used my converged result from first order simplefoam as initial guess. I only changed divergent schemes in simplefoam to increase the order. I put them at the end of this thread. (only the last one worked)

I tried icofoam but courant number diverged after some time. My case is laminar. I used my converged result from first order simplefoam as initial guess. I would be very greatfull if someone help me to solve my problem, because I have been working on this for long time.

I tried the schemes below:
divSchemes
{
default none;
div(phi,U) Gauss linearUpwind grad(U);
div(phi,k) Gauss linear;
div(phi,epsilon) Gauss linear;
div(phi,R) Gauss linear;
div(R) Gauss linear;
div(phi,nuTilda) Gauss linear;
div((nuEff*dev(T(grad(U))))) Gauss linear;
}
divSchemes
{
default none;
div(phi,U) Gauss linear;
div(phi,k) Gauss linear;
div(phi,epsilon) Gauss linear;
div(phi,R) Gauss linear;
div(R) Gauss linear;
div(phi,nuTilda) Gauss linear;
div((nuEff*dev(T(grad(U))))) Gauss linear;
}
,divSchemes
{
default none;
div(phi,U) Gauss SFCD;
div(phi,k) Gauss linear;
div(phi,epsilon) Gauss linear;
div(phi,R) Gauss linear;
div(R) Gauss linear;
div(phi,nuTilda) Gauss linear;
div((nuEff*dev(T(grad(U))))) Gauss linear;
}
divSchemes
{
default none;
div(phi,U) Gauss limitedLinearV 1;
div(phi,k) Gauss limitedLinear 1;
div(phi,epsilon) Gauss limitedLinear 1;
div(phi,R) Gauss limitedLinear 1;
div(R) Gauss linear ;
div(phi,nuTilda) Gauss limitedLinear 1;
div((nuEff*dev(T(grad(U))))) Gauss linear;
}
divSchemes
{
default none;
div(phi,U) Gauss QUICKV leastSquares;
div(phi,k) Gauss linear;
div(phi,epsilon) Gauss linear;
div(phi,R) Gauss linear;
div(R) Gauss linear;
div(phi,nuTilda) Gauss linear;
div((nuEff*dev(T(grad(U))))) Gauss linear upwind;
}
divSchemes
{
default none;
div(phi,U) Gauss linearUpwindV leastSquares;
div(phi,k) Gauss linear;
div(phi,epsilon) Gauss linear;
div(phi,R) Gauss linear;
div(R) Gauss linear;
div(phi,nuTilda) Gauss linear;
div((nuEff*dev(T(grad(U))))) Gauss linear upwind;
}

I couldnt attach my case file so I am attaching my residualsi checkmesh results and BCs.

0/p
dimensions [0 2 -2 0 0 0 0];

internalField uniform 0;

boundaryField
{
wall
{
type zeroGradient;
}

airfoil
{
type zeroGradient;
}


sides
{
type freestreamPressure;
}


}
0/U
dimensions [0 1 -1 0 0 0 0];

internalField uniform (1 0 0);

boundaryField
{
wall
{
type fixedValue;
value uniform (0 0 0);
}

airfoil
{
type fixedValue;
value uniform (0 0 0);
}


sides
{
type freestream;
freestreamValue uniform (1 0 0);
}


}
Time = 0

Mesh stats
points: 370455
faces: 4159775
internal faces: 4037721
cells: 2049374
boundary patches: 3
point zones: 0
face zones: 0
cell zones: 0

Overall number of cells of each type:
hexahedra: 0
prisms: 0
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 2049374
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
airfoil 72504 36528 ok (non-closed singly connected)
sides 2470 1393 ok (non-closed singly connected)
wall 47080 23974 ok (non-closed singly connected)

Checking geometry...
Overall domain bounding box (-0.85 -0.5 -1.66533e-16) (1.05 0.5 0.27)
Mesh (non-empty, non-wedge) directions (1 1 1)
Mesh (non-empty) directions (1 1 1)
Boundary openness (-1.59378e-17 6.14025e-17 -3.65029e-15) OK.
Max cell openness = 3.74888e-16 OK.
Max aspect ratio = 6.7235 OK.
Minumum face area = 3.48265e-09. Maximum face area = 0.00154965. Face area magnitudes OK.
Min volume = 9.66928e-14. Max volume = 2.01324e-05. Total volume = 0.512781. Cell volumes OK.
Mesh non-orthogonality Max: 58.2936 average: 19.726
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 0.715771 OK.
Coupled point location match (average 0) OK.

Mesh OK.

End


Thank you
Attached Images
File Type: png simplefirst.png (28.4 KB, 18 views)
File Type: png simplesecond.png (58.6 KB, 17 views)
File Type: png ico.png (28.2 KB, 18 views)
File Type: png airfoil1.png (115.6 KB, 17 views)
File Type: png airfoil2.png (98.0 KB, 16 views)
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Old   September 10, 2015, 08:20
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Philipp
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1st order has more numerical dissipation than 2nd order, i.e. you spuriously solve for a case with artificially higher viscosity. Also, you damp all kinds of effects by 1st order schemes. Maybe your case just isn't stationary, which only appears in 2nd order?

Edit: Ok, you should post the whole schemes file and also the fvOptions. And some log output would be beneficial. Please use the "code" button (under "->Go Advanced') to post code - don't just copy it to the text box.
Also: Why do you specify all the different div-Schemes for a laminar case? This is pretty confusing.
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