Register Blogs Members List Search Today's Posts Mark Forums Read

 April 8, 2008, 09:13 Hi, I have a 2D case with m #1 New Member   Anita K. Join Date: Mar 2009 Posts: 25 Rep Power: 9 Hi, I have a 2D case with mesh generation with blockMesh. The solver didn't solve momentum (U) equation. According to this thread http://www.cfd-online.com/OpenFOAM_D...es/1/6884.html my domain is bent. I analyzed my mesh and found the problematic block. In this block I use edgeGrading. If I change all ratios to 1 the block is straight. When using combinations of ratios the block gets fatter in the middle. Parts from blockMeshDict: convertToMeters 0.001; //mm vertices ( //a (-31.7 9 -0.5) // Vertex a1b = 0 (0.0 9 -0.5) // Vertex a2b = 1 (0.0 15.775 -0.5) // Vertex a3b = 2 (-31.7 15.775 -0.5) // Vertex a4b = 3 (-31.7 9 0.5) // Vertex a1t = 4 (0.0 9 0.5) // Vertex a2t = 5 (0.0 15.775 0.5) // Vertex a3t = 6 (-31.7 15.775 0.5) // Vertex a4t = 7 ); blocks ( hex (0 1 2 3 4 5 6 7) (50 22 1) edgeGrading (0.25 1 1 0.25 1 4 4 1 1 1 1 1 )//block a ); CheckMesh: (on z-axis the define points are at -0.5 mm or 0.5 mm) Checking geometry... Domain bounding box: (-0.0317 0.009 -0.000515173) (0 0.015775 0.000515173) Boundary openness (1.90575e-18 -4.52277e-17 2.57335e-16) OK. Max cell openness = 2.22755e-16 OK. Max aspect ratio = 7.16218 OK. Minumum face area = 4.29135e-08. Maximum face area = 1.16818e-06. Face area magnitudes OK. Min volume = 4.29163e-11. Max volume = 3.55129e-10. Total volume = 2.17623e-07. Cell volumes OK. Mesh non-orthogonality Max: 43.2975 average: 31.2745 Non-orthogonality check OK. Face pyramids OK. Max skewness = 0.418386 OK. Min/max edge length = 0.000141259 0.00116818 OK. All angles in faces OK. Face flatness (1 = flat, 0 = butterfly) : average = 1 min = 1 All face flatness OK. Mesh OK. Is this a bug with edgeGrading? Anita

 April 8, 2008, 10:50 Sorry, I don't see the problem #2 Senior Member   Hrvoje Jasak Join Date: Mar 2009 Location: London, England Posts: 1,781 Rep Power: 22 Sorry, I don't see the problem: "the block gets fatter in the middle". Can I see this from the picture above? I originally wrote all this grading stuff, it is used in the pitzDaily simpleFoam tutorial and it works in 2-D without trouble. Can you investigate further? Hrv __________________ Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk

 April 9, 2008, 02:55 Hi Hrv, you don't see it from #3 New Member   Anita K. Join Date: Mar 2009 Posts: 25 Rep Power: 9 Hi Hrv, you don't see it from the above picture. I added two pictures looking sideways on the mesh. The z-axis is stretched to see the curved surface better. You can also see it from the Domain bounding box (-0.0317 0.009 -0.000515173) (0 0.015775 0.000515173) which is larger in z direction as the hex in blockMeshDict. I also looked in the points file: Only few point at the start and the end of the file have the desired z-position. Anita Looking from right side: Looking from the bottom:

 April 9, 2008, 05:09 Hi, I looked at the utilitis #4 New Member   Anita K. Join Date: Mar 2009 Posts: 25 Rep Power: 9 Hi, I looked at the utilitis of OpenFoam and found flattenMesh. This removed the curved surface and now my mesh is real 2D. Also the solver now solves the U-equation. By now I can go on with simulating my case, but I still want to now if it was my fault and how I can avoid this problem in future. Anita

 December 11, 2008, 07:43 Hallo Anita, I have the sam #5 Senior Member   Wolfgang Heydlauff Join Date: Mar 2009 Location: Germany Posts: 136 Rep Power: 10 Hallo Anita, I have the same problem that by using the edgeGrading the bounding box gets greater. flattenMesh does NOT remove it, poorly. And further advice?

 February 26, 2009, 10:36 Hi, I can also confirm this #6 New Member   Andreas Feymark Join Date: Mar 2009 Location: Gothenburg, Sweden Posts: 18 Rep Power: 9 Hi, I can also confirm this behavior for my 3D-cylinder. /Andreas

 February 27, 2009, 11:38 For my case the error comes an #7 New Member   Andreas Feymark Join Date: Mar 2009 Location: Gothenburg, Sweden Posts: 18 Rep Power: 9 For my case the error comes and goes depending on what value I use on the edge. A value less than 12.5 for instance gives bad behavior and a value greater than 13.2 works well. Hrv, do you have any clue why this error might occur? /Andreas

 March 2, 2009, 12:16 A blockMeshDict like the one b #8 New Member   Andreas Feymark Join Date: Mar 2009 Location: Gothenburg, Sweden Posts: 18 Rep Power: 9 A blockMeshDict like the one below creates this error. The vertices are ordered according to http://www.opencfd.co.uk/openfoam/doc/blockMesh.html . /*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \ / O peration | Version: 1.5 | | \ / A nd | Web: http://www.OpenFOAM.org | | \/ M anipulation | | /*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object blockMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // convertToMeters 1; vertices ( ( 0 0 0 ) // vertex number 0 ( 1 0 0 ) // vertex number 1 ( 1 1 0 ) // vertex number 2 ( 0 1 0 ) // vertex number 3 ( 0 0 1 ) // vertex number 4 ( 1 0 1 ) // vertex number 5 ( 1 1 1 ) // vertex number 6 ( 0 1 1 ) // vertex number 7 ); blocks ( hex (0 1 2 3 4 5 6 7) (2 2 2) edgeGrading (4 3 3 4 2 1 1 2 1 1 1 1) ); edges ( ); patches ( ); mergePatchPairs ( ); // ************************************************** *********************** // /Andreas

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules