# Usage of polyDualMesh utility

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 January 21, 2011, 03:40 Usage of polyDualMesh utility #1 Senior Member   Join Date: Feb 2010 Posts: 213 Rep Power: 8 I can't find documentation or examples about polyDualMesh, I only read a very few posts here about this meshing utility. My aim is to convert a tet mesh into a polyhedral one, in order to lower the large amount of cells I obtain with tetrahedrals. I didn't understand the concrete meaning of the parameter and why most of users set it between 40 and 80. Please, can anyone explain that?

 January 21, 2011, 10:43 #2 Senior Member   Olivier Join Date: Jun 2009 Location: France, grenoble Posts: 242 Rep Power: 9 helllo, I am not sure about feature angle, but this help to keep mesh on curved surfaces, so on a cube, 90 would work, and on more complexe geom, less. I am using it in the 60-80 range. Check the -concaveMultiCells option, because this help the give you a correct mesh, and don't forget du check the mesh after ! regards, olivier

 January 21, 2011, 10:54 #3 Senior Member   Join Date: Feb 2010 Posts: 213 Rep Power: 8 I know the feature angle is important in obtaining a good mesh, but I'd like to understand the exact meaning to use the utility well. I hope someone else will reply here. Anyway, thanks for your suggestion about best angle range and above all the -concaveMultiCells option: I haven't ever heard about it. How do I use it and how it works? Something like Code: `polyDualMesh 75 -concaveMultiCells`

 January 28, 2011, 03:52 #4 Senior Member   Join Date: Feb 2010 Posts: 213 Rep Power: 8 Any reply? Anyway, I read someone uses Code: `polyDualMesh 180` What does it mean? It's quite out of common ranges, I need to understand the concrete meaning of the angle parameter.

January 28, 2011, 08:07
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Quote:
 Originally Posted by vaina74 Any reply? Anyway, I read someone uses Code: `polyDualMesh 180` What does it mean? It's quite out of common ranges, I need to understand the concrete meaning of the angle parameter.
Try

polyDualMesh -doc

that should open the browser with the Doxygen-documentation of the browser. Go to the source-file polyDualMeshApp.C. The description of the options and arguments is there

 January 28, 2011, 10:52 #6 Senior Member   Join Date: Feb 2010 Posts: 213 Rep Power: 8 OK. polyDualMesh -doc doesn't open anything, i think i miss documentation because of my installation settings. anyway, I look for polyDualMeshApp.C and i found a bare file (i use OF-1.5-dev). well, i didn't give up, i tried with OF-1.7 and found a more complex and detailed file, but i can read only: Code: ``` - polyDualMesh featureAngle Detects any boundary edge > angle and creates multiple boundary faces for it. Normal behaviour is to have each point become a cell (1.5 behaviour)``` i don't think that's helpful, unleass you mean i must get deep inside the code.

 January 31, 2011, 03:41 #7 Senior Member   Join Date: Feb 2010 Posts: 213 Rep Power: 8 I found some documentation about tet mesh conversion into polyhedral one. It concerns other software or general algorithms, but I hope I can understand anyway. Polyhedral conversion process joins quad faces (derived from tet cells): below a feature angle (between normals?) the edge between two faces is ignored, above a feature angle the edge is retained. Am I correct? Anyway a feature angle of 180° looks strange to me.

 June 8, 2015, 06:39 polyDualMesh Problem #8 New Member   Join Date: Jun 2015 Posts: 1 Rep Power: 0 Hi, I am new here ;-) I have a problem with polyDualMesh. I am workin with OpenFoam. I have a 2D flow passag with step. I create the mesh with GMesh. So it is a tetrahedral mesh. When I'm now execute the command polyDualMesh. The programm creates the new Mesh but it looks like the picture one. Now I found on the openfoam-wiki a tuorial: https://openfoamwiki.net/index.php/P...esh_generation There the mesh has two layer in the third dimension. My mesh has this too. Picture two On the openfoam-wiki website there are step 5 to 7 how to make a good mesh. But on step 5 you have to trn the setSet application to create a cell set that contains only one layer of cells. That's my problem. How to execute the setSet comand . Can anybody tell me how it works? How the command look like. Thank you very very much for help!

 October 23, 2015, 14:38 #9 New Member   toor Join Date: Oct 2015 Posts: 1 Rep Power: 0 Hi folk, I have worked with generating primal and/or dual meshes. When deriving dual-mesh around each primal-mesh (tet mesh) point a dual-cell is constructed. For interior points constructing dual is straight forward, however for boundary points defining ridges and/or corners to be represented by dual-cell faces they must be split along these entities. A ridge is an edge of primal mesh separating two different sides of the domain being meshed. To decide which boundary edges are ridges, a calculation of angles between faces sharing(dihedral angle) is required, i.e. for a simple cube with straight sides you can say that if dihedral angle between faces is not 180 (or 0) then edge shared between the faces is a ridge. Corners are the points where more than two ridges meet. I hope this makes sense. Last edited by toor; October 23, 2015 at 17:22.

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