| AMR96 |
April 6, 2023 11:08 |
Conversion problem with simpleFoam
1 Attachment(s)
Hello,
I am new to OF, I'm trying to simulate external flow around an Ahmed body and I am having convergence problems. Initially, I ran the simulation on Ansys and it worked fine with good results. I decided to use the same mesh for OF.
The main problem is that when I use second order schemes, the residuals start decreasing but after a while they stall and start to increase again. This is specially the case with the pressure residual. In addition to residuals, I am also using drag and lift coefficients to monitor the results and those values are also incorrect.
I am using Realizable k-epsilon with wall functions to run the simulation since this was the same algorithm that I ran in Ansys. I also tried k-omega sst but that didn't work either.
I have also tried running the simulation with first order schemes until the residuals are low enough and then changing to second order scheme but unfortunately the same residual behaviour was observed as before.
The mesh quality is not bad as you can see in the checkMesh report below. I have set the nNonOrthogonalCorrectors to 2 in order to addresse the high non-orthogonality.
I would really appreciate any help as I have been trying different schemes and workarounds to make this simulation work for the last three weeks. I am really out of ideas.
The BC file is also attached to the post.
Code:
Mesh stats
points: 676066
internal points: 623321
faces: 6958333
internal faces: 6857479
cells: 3393943
faces per cell: 4.070726
boundary patches: 6
point zones: 0
face zones: 1
cell zones: 1
Overall number of cells of each type:
hexahedra: 0
prisms: 240040
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 3153903
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 581 361 ok (non-closed singly connected)
ground_slip 1174 645 ok (non-closed singly connected)
ground 24242 12465 ok (non-closed singly connected)
outlet 581 361 ok (non-closed singly connected)
symmetry 51684 28609 ok (non-closed singly connected)
car 22592 11462 ok (non-closed singly connected)
Checking faceZone topology for multiply connected surfaces...
FaceZone Faces Points Surface topology
interior-geom-1-enclosure_enclosure6857479 676065 multiply connected (shared edge)
<<Writing 675152 conflicting points to set nonManifoldPoints
Checking basic cellZone addressing...
CellZone Cells Points Volume BoundingBox
geom-1-enclosure_enclosure 3393943 676066 19.579551 (-1.1268994 -0.7405 -7.448) (0.27310058 0.1945 7.552)
Checking geometry...
Overall domain bounding box (-1.1268994 -0.7405 -7.448) (0.27310058 0.1945 7.552)
Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
Mesh has 3 solution (non-empty) directions (1 1 1)
Boundary openness (1.3906281e-15 -4.1996552e-16 -8.38449e-18) OK.
Max cell openness = 4.2124307e-16 OK.
Max aspect ratio = 7.2929552 OK.
Minimum face area = 2.965643e-07. Maximum face area = 0.0050927999. Face area magnitudes OK.
Min volume = 1.342751e-10. Max volume = 0.00014501842. Total volume = 19.579551. Cell volumes OK.
Mesh non-orthogonality Max: 64.770132 average: 15.500522
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 2.3385037 OK.
Coupled point location match (average 0) OK.
fvsolution:
Code:
solvers
{
p
{
solver GAMG;
smoother GaussSeidel;
tolerance 1e-7;
relTol 0.01;
}
Phi
{
$p;
}
U
{
solver smoothSolver;
smoother GaussSeidel;
tolerance 1e-8;
relTol 0.1;
nSweeps 1;
}
k
{
solver smoothSolver;
smoother GaussSeidel;
tolerance 1e-15;
relTol 0.1;
nSweeps 1;
}
epsilon
{
solver smoothSolver;
smoother GaussSeidel;
tolerance 1e-12;
relTol 0.1;
nSweeps 1;
}
}
SIMPLE
{
nNonOrthogonalCorrectors 2;
consistent yes;
}
potentialFlow
{
nNonOrthogonalCorrectors 10;
}
relaxationFactors
{
equations
{
U 0.7;
k 0.5;
omega 0.5;
}
}
cache
{
grad(U);
}
// ************************************************************************* //
fvscheme:
Code:
ddtSchemes
{
default steadyState;
}
gradSchemes
{
default leastSquares;
grad(U) leastSquares;
}
divSchemes
{
default none;
div(phi,U) bounded Gauss linearUpwindV grad(U);
div(phi,k) Gauss linearUpwind grad(k);
div(phi,epsilon) Gauss linearUpwind grad(epsilon);
div((nuEff*dev2(T(grad(U))))) Gauss linear;
}
laplacianSchemes
{
default Gauss linear corrected;
}
interpolationSchemes
{
default linear;
}
snGradSchemes
{
default corrected;
}
wallDist
{
method meshWave;
}
// ************************************************************************* //
|
