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-   -   PotentialFoam few problems (http://www.cfd-online.com/Forums/openfoam-solving/58714-potentialfoam-few-problems.html)

chris_sev July 16, 2008 06:54

Hallo, I'm trying to run si
 
Hallo,

I'm trying to run simulation in openFoam. It's an external flow around particular shape. I used fluentMeshToFoam to convert mesh, which has been done in HyperMesh. Firstly I dealed with potentialFoam solver (according to other users advices which I found in this forum).
I performed simulation but results are wrong. When I run ParaView to check velocity distribution nothing seems to happened there. Whole model is blue which means velocity is zero everywhere. I'm wondering what I did wrong. I went through all dictionary files once again but In my opinion everything is fine. I applied boundary conditions correctly. I'm not pretty sure how solution schemes work (I've just began playing with OF) so I have considered different scenarios but always with the same results.

Thought there might be something wrong with the mesh. I have run checkMesh but I'm not sure what's the explanation of those results. Could you please have a look on it:

--------------------------------------------------------------------
Create polyMesh for time = constant

Time = constant

Mesh stats
points: 373149
edges: 2289739
faces: 3709523
internal faces: 3590683
cells: 1792916
boundary patches: 6
point zones: 0
face zones: 0
cell zones: 0

Number of cells of each type:
hexahedra: 0
prisms: 124346
wedges: 0
pyramids: 4196
tet wedges: 0
tetrahedra: 1664374
polyhedra: 0

Checking topology...
Boundary definition OK.
Point usage OK.
Upper triangular ordering OK.
Topological cell zip-up check OK.
Face vertices OK.
Face-face connectivity OK.
Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces ...
Patch Faces Points Surface
inlet 260 154 ok (not multiply connected)
outlet 260 154 ok (not multiply connected)
wall_side 720 418 ok (not multiply connected)
wall_water 20152 10270 ok (not multiply connected)
wall_top 1156 610 ok (not multiply connected)
wall_ship 96292 49038 ok (not multiply connected)

Checking geometry...
Domain bounding box: (-1.82397e+06 -1.32002e+06 8294.26) (1.80603e+06 1.3199
8e+06 593733)
Boundary openness (9.88848e-18 9.87072e-18 1.38914e-16) OK.
***High aspect ratio cells found, Max aspect ratio: 110560, number of cells 1
<<Writing 1 cells with high aspect ratio to set highAspectRatioCells
Minumum face area = 361.351. Maximum face area = 4.56545e+10. Face area mag nitudes OK.
Min volume = 212.664. Max volume = 3.14113e+15. Total volume = 5.60991e+18. Cell volumes OK.
Mesh non-orthogonality Max: 87.7938 average: 21.4714
*Number of severely non-orthogonal faces: 9750.
Non-orthogonality check OK.
<<Writing 9750 non-orthogonal faces to set nonOrthoFaces
Face pyramids OK.
***Max skewness = 10.2348, 2 highly skew faces detected which may impair the qu ality of the results
<<Writing 2 skew faces to set skewFaces
Min/max edge length = 6.34815 377938 OK.
All angles in faces OK.
Face flatness (1 = flat, 0 = butterfly) : average = 0.997814 min = 0.809597
All face flatness OK.

Failed 2 mesh checks.

End
-------------------------------------------------------------------------------- ---


It says 'Failed 2 mesh checks.' It founds 1 cell with high aspect ratio 110560. This value is definitely to high. I've checked this mesh in HyperMesh and for this particular cell value of max aspect ratio is 1.8, so what's the reason of the discrepancy between OF and HM?

There are also two faces with highly skew. And again there's nothing wrong with those faces in HM.

What do you think about this? Do you think the fact that 'Failed 2 mesh checks.' could be the reason of my problems with results? In my opinion I should obtain some velocity distribution, probably wrong in areas which were pointed by checkMesh, but I shouldn't get zero everywhere.

thanks in advance!

Chris

chris_sev July 22, 2008 10:15

hi, I messed with initial v
 
hi,

I messed with initial values. I found a problem and performed few more simulations. Now, velocity distribution looks much more better but values of maximum velocity fluctuates between 569 and 1260 m/s (depending on pressure solver type), when initial velocity is 19.97 m/s. Lowest values (569) I have obtained for smoothSolver with GaussSeidel smoother. But honestly I have no idea what else could be improved. I really must to work with this mesh. I didn't met any problems dealing with this in CFX. What do you think about this, is there any way in OpenFOAM to handle with my mesh and my case? Maybe I should exploit the potential of smoothSolver, but how?
I would be very appreciate for any hints.!!!
thank you!!!

chris


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