<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Dear gmsh community,<div class=""><br class=""></div><div class="">Currently I am working on a part of an airfoil which has a ridge of 5 mm on the trailing edge. Please see the attached screenshot. I mesh the surface in enGrid and lateron I create an extrusion on that surface of an absolute height of 20 mm. On that extrusion I build a volume tet mesh with gmsh. </div><div class=""><img apple-inline="yes" id="A5FEACF1-2251-43CB-B140-BC2147E9E9E2" height="313" width="364" apple-width="yes" apple-height="yes" src="cid:539B29C5-5913-405E-9C0E-508D04D18BD7@dg-flugzeugbau.local" class=""></div><div class="">I finally got it to work but after I converted the mesh to OpenFOAM with gmshToFoam, checkMesh complain about some bad quality cells. Please see the following output:</div><div class=""><br class=""></div><div class=""><CODE></div><div class=""><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">Kates-MacBook-Pro:geometry kate$ checkMesh</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">/*---------------------------------------------------------------------------*\</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">| ========= | |</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">| \\ / O peration | Version: 2.3.1 |</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">| \\ / A nd | Web: <a href="http://www.OpenFOAM.org" class="">www.OpenFOAM.org</a> |</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">| <a href="smb:///" class="">\\/</a> M anipulation | |</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">\*---------------------------------------------------------------------------*/</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">Build : 2.3.1-262087cdf8db</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">Exec : checkMesh</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">Date : Jul 23 2015</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">Time : 16:58:31</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">Host : "Kates-MacBook-Pro.local"</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">PID : 70687</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">Case : /Users/kateeisenhower/Documents/gmsh/Data/geometry</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">nProcs : 1</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">fileModificationChecking : Monitoring run-time modified files using timeStampMaster</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">allowSystemOperations : Allowing user-supplied system call operations</div><div style="margin: 0px; font-size: 11px; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">Create time</div><div style="margin: 0px; font-size: 11px; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">Create polyMesh for time = 0</div><div style="margin: 0px; font-size: 11px; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">Time = 0</div><div style="margin: 0px; font-size: 11px; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">Mesh stats</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> points: 680409</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> faces: 5884664</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> internal faces: 5515361</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> cells: 2760292</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> faces per cell: 4.13001</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> boundary patches: 2</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> point zones: 0</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> face zones: 1</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> cell zones: 1</div><div style="margin: 0px; font-size: 11px; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">Overall number of cells of each type:</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> hexahedra: 0</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> prisms: 358857</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> wedges: 0</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> pyramids: 0</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> tet wedges: 0</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> tetrahedra: 2401435</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> polyhedra: 0</div><div style="margin: 0px; font-size: 11px; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">Checking topology...</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> Boundary definition OK.</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> Cell to face addressing OK.</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> Point usage OK.</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> Upper triangular ordering OK.</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> Face vertices OK.</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> Number of regions: 1 (OK).</div><div style="margin: 0px; font-size: 11px; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">Checking patch topology for multiply connected surfaces...</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> Patch Faces Points Surface topology </div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> patch0 368444 184719 ok (non-closed singly connected) </div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> defaultFaces 859 754 multiply connected (shared edge) </div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> <<Writing 286 conflicting points to set nonManifoldPoints</div><div style="margin: 0px; font-size: 11px; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">Checking geometry...</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> Overall domain bounding box (-3 -0.501511 -3) (3 0.501988 3)</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> Mesh (non-empty, non-wedge) directions (1 1 1)</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> Mesh (non-empty) directions (1 1 1)</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> Boundary openness (1.30587e-19 2.76155e-16 2.35201e-16) OK.</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> Max cell openness = 5.12735e-16 OK.</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> Max aspect ratio = 45.2301 OK.</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> Minimum face area = 1.53274e-09. Maximum face area = 0.566488. Face area magnitudes OK.</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> Min volume = 1.13287e-09. Max volume = 0.102629. Total volume = 35.889. Cell volumes OK.</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> Mesh non-orthogonality Max: 178.031 average: 14.488</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> *Number of severely non-orthogonal (> 70 degrees) faces: 384.</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> ***Number of non-orthogonality errors: 26.</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> <<Writing 410 non-orthogonal faces to set nonOrthoFaces</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> ***Error in face pyramids: 307 faces are incorrectly oriented.</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> <<Writing 304 faces with incorrect orientation to set wrongOrientedFaces</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> ***Max skewness = 211.421, 8 highly skew faces detected which may impair the quality of the results</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> <<Writing 8 skew faces to set skewFaces</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> Coupled point location match (average 0) OK.</div><div style="margin: 0px; font-size: 11px; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">Failed 3 mesh checks.</div><div style="margin: 0px; font-size: 11px; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">End</div></div><div class=""><br class=""></div><div class=""></CODE></div><div class=""><br class=""></div><div class="">Especially the 286 conflicting points (nonManifoldPoints), the non-orthogonal faces and the faces with incorrect orientation bother me. I checked the problematic faces in ParaView and the problematic cells are all in the area around the ridge. However I didn’t know how to locate the nonManifoldPoints but I guess they are also located in this place.</div><div class="">I think there are a few possible solutions now:</div><div class=""><br class=""></div><div class="">1) Make one sharp edge instead of the two edges which form the trailing edge</div><div class="">2) Mesh the ridge surface mesh with smaller elements</div><div class="">3) Mesh the ridge surface mesh with bigger elements</div><div class="">4) Make a a radius instead of a ridge</div><div class=""><br class=""></div><div class="">All of these options would be okay for me. Which method would you recommend for meshing a trailing edge? And which element size would you recommend?</div><div class=""><br class=""></div><div class="">If someone has any other idea I would be very grateful if you could share it. How is this kind of problem handled usually?</div><div class=""><br class=""></div><div class="">Best regards and thanks in advance,</div><div class=""><br class=""></div><div class="">Kate</div><div class=""><br class=""></div><div class="">P.S.: If you need any further information please don’t hesitate to ask!</div></body></html>