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[snappyHexMesh] 2D Cylinder mesh problems with Snappy |
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April 27, 2011, 12:16 |
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#21 |
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RDG
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Right now I'm not at work so I can't post it, but I can tell it fails with an error of different areas in faces of cells on the boundary of the processors. Something like
"face # area does not match neighbour # by %" |
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April 27, 2011, 12:23 |
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#22 |
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Sounds like a boundary mismatch. Anyway, post it when you have a chance.
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April 27, 2011, 13:52 |
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#23 |
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RDG
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I don't get what you mean by "boundary mismatch".
If I run the case without decomposing it, it runs without any errors. If I run it decomposing it first, it gives the error you can see in the log attached. Thanks. |
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April 27, 2011, 16:06 |
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#24 |
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I ran it serial and it went okay except for some weird faces in your borde_ataqe and borde_salida regions. The ones in the jpg are for the trailing edge on the Front plane. There area few others. I think they are not connecting properly with their equivalent faces between the Front and Back planes. Their general location corresponds to the error reported in your log file.
There are some warnings in your log file regarding possible wedges between the Front and Back planes as well. Might be related... Code:
--> FOAM Warning : From function twoDPointCorrector::twoDPointCorrector(const polyMesh& mesh, const vector& n) in file twoDPointCorrector/twoDPointCorrector.C at line 168 The number of points in the mesh is not equal to twice the number of edges normal to the plane - this may be OK only for wedge geometries. Please check the geometry or adjust the orthogonality tolerance. Oh yeah, the trailing edge is warped too in the z direction but this won't matter once you extrude as per the procedure I suggested above. It's the snappy bug for CAD edges but apparently they fixed it in the next release. |
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April 28, 2011, 11:31 |
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#25 |
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Ran it in parallel and snappyHexMesh finishes similarly to the serial run. The mesh also fails two checkMesh tests in both serial and parallel.
Code:
***Number of edges not aligned with or perpendicular to non-empty directions: 38872 ***Max skewness = 5.30239, 32 highly skew faces detected which may impair the quality of the results |
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April 28, 2011, 11:39 |
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#26 |
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How did you run it in parallel?
I always get the same error. I've tried a few combinations, even without the boxes and always fails. |
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April 28, 2011, 11:47 |
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#27 |
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April 28, 2011, 11:53 |
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#28 |
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RDG
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I think you have to do
mpirun -np snappyHexMesh -parallel so it really runs it in parallel. Am I wrong? |
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April 28, 2011, 12:07 |
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#29 |
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That's how I run all my OF executables in parallel for OpenMPI. Use it and you'll see that it works. I just tried the -parallel option and it failed like it did for you. They provide this option in the user guide for 1.7.x but I am not sure when it was introduced. Personally I never used it. You might want to search the forum on this topic.
Anyway, both parallel and serial checkMesh fail so the problem is in the specific settings at the leading/trailing edges. I am not sure but I think I've seen something like this a few months ago with snappy when preparing the 2D procedure. A simpler refinement box around the entire airfoil and extending to the exit plane could work better. |
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April 28, 2011, 12:26 |
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#30 |
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By the way you don't have to reconstruct your parallel case anymore. Just process it as you would a serial run. That part of the user guide is outdated.
Definitely skip the -parallel option. It might actually be the (very) old way of doing things. |
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April 28, 2011, 12:48 |
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#31 |
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That way you don't to decompose your case either. I don't think that's the right way of doing it.
http://www.cfd-online.com/Forums/ope...-parallel.html |
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April 28, 2011, 12:54 |
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#32 |
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It's up to you. All I can tell you is that -parallel is not needed and it's been a while that you don't have to reconstruct your case anymore. Used to be like that with the older parallel implementation but not anymore.
Wouldn't hurt to try it |
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April 28, 2011, 13:11 |
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#33 |
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Ok, I just tried and it does not work the way you say.
It takes the same time to perform, and twice the ram. It is say doing both processors perform the same case. It even works without decomposing. |
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April 28, 2011, 14:32 |
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#34 |
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Oops my bad! Just checked our execution scripts and it is implemented with the -parallel option.
Last edited by ziad; April 29, 2011 at 15:51. |
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July 19, 2011, 02:17 |
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#35 |
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Hi all,
I've been reading through this topic and practicing a bit on the method discribed by Ziad but I struggle to understand one thing: In order to create the 2D mesh starting from a sHM mesh, we need to make a 3D mesh with the face of interest that has sufficiently enough cells to be usefull to us. So for example, in my case, I need to mesh a foil section with about 4M cells to obtain a mere 140k cells once 2d'ed. Am I missing something there or is is there a way to avoid spending a fair bit of time making a big mesh to get a dumb coarse 2D mesh? Thanks, |
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January 4, 2012, 09:57 |
extrudeMesh
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#36 |
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Nick
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The method for me does not seem to work. I have tried to find a solution. To no avail. The problem is as follows:
I am trying to model a multi element wing cross section. First I create the blockMesh and run sHM in parallel. Subsequently I use reconstructParMesh to view it in paraview. In paraview it looks good. Then I copy the polyMesh directory from time3 to constant and I run extrudeMesh. However it does not create new patches. Needless to say, autoPatch does not work either. My model is in the y-z plane. However I don't quite understand how to edit the extrudeMeshDict so that it works. (I am assuming this is the same file as the extrudeProperties file posted by ziad?) I did try several combinations of the wedge properties, but this did not help. Any thoughts? Thanks in advance, Nick |
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January 4, 2012, 17:03 |
OpenFOAM version
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#37 |
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Nick
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Apologies I forgot to mention OF and ubuntu version. I am running OF 2.01 (I think, the latest version in the ubuntu software center) and Ubuntu 11.04.
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June 4, 2012, 15:49 |
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#38 | |
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Quote:
Code:
// What to extrude: // patch : from patch of another case ('sourceCase') // mesh : as above but with original case included // surface : from externally read surface //constructFrom mesh; USE THIS TO EXTEND A 3D MESH BY EXTRUSION. MESHES ARE AUTOMATICALLY STITCHED TOGETHER!!! constructFrom patch; // If construct from patch/mesh: sourceCase "./"; sourcePatches (floor); // If construct from patch: patch to use for back (can be same as sourcePatch) exposedPatchName floor; // Flip surface normals before usage. flipNormals false; //- Linear extrusion in point-normal direction extrudeModel linearNormal; nLayers 30; expansionRatio 1.0; //0.9; linearNormalCoeffs { thickness 0.3; } // Do front and back need to be merged? Usually only makes sense for 360 // degree wedges. mergeFaces false; //true; // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // Last edited by ziad; June 5, 2012 at 02:00. |
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Tags |
2d mesh, airfoil, cylinder, extrudemesh, snappyhexmesh |
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