<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><br class=""><blockquote type="cite" class="">On 24 Mar 2016, at 12:27, Bernd Hahnebach <<a href="mailto:gmsh@b75.ch" class="">gmsh@b75.ch</a>> wrote:<br class=""><br class="">Hi GMSH users and developers,<br class=""><br class="">Is it possible to check a mesh in gmsh in the regard of negative jacobians? If yes, is it possible to show such elements in gmsh gui? </blockquote><div class=""><br class=""></div><div class="">Yes (see attached picture):</div><div class=""><br class=""></div><div class="">- Load your mesh</div><div class="">- Open Tools->Plugins->AnalyzeCurvedMesh</div><div class="">- Select "0" in the first option (to compute the Jacobian determinant J and plot min(J))</div><div class=""><br class=""></div><div class="">To accurately visualize the curved grid (and post-processing dataset):</div><div class=""><br class=""></div><div class="">- Select "Adapt visualization grid" in the view options ("General" tab)</div><div class="">- Increase the "High-order element subdvisions" in the mesh options ("Aspect" tab)</div><div class=""><br class=""></div><div class="">This can all be scripted of course.</div><div class=""><br class=""></div><div class="">The calculation method is described in the following paper:</div><div class=""><br class=""></div><div class="">Johnen, A., Remacle, J. F., & Geuzaine, C. (2013). Geometrical validity of curvilinear finite elements. Journal of Computational Physics, 233, 359-372. <a href="http://gmsh.info/doc/preprints/gmsh_curved_preprint.pdf" class="">http://gmsh.info/doc/preprints/gmsh_curved_preprint.pdf</a></div><div class=""><br class=""></div><div class="">Christophe</div><div class=""><br class=""></div><div class=""><img apple-inline="yes" id="45D0BCD2-D6AD-4317-BD63-10E38DE22FA5" height="895" width="898" apple-width="yes" apple-height="yes" src="cid:9DA04FA5-5220-44AF-AFFA-81F8309B212B@home" class=""></div><div class=""><br class=""></div><br class=""><blockquote type="cite" class="">Attached a mesh wich has negative jacobians to test with.<br class=""><br class="">mesh: Shape_mesh_negative_jacobian.unv.zip (remove .zip)<br class=""><a href="http://forum.freecadweb.org/download/file.php?id=21583&sid=a7b68cea7fa02126487316248b875c2d" class="">http://forum.freecadweb.org/download/file.php?id=21583&sid=a7b68cea7fa02126487316248b875c2d</a><br class=""><br class=""><br class="">What is the recommended way to avoid such negative jacobians? Attached the geometry of the mesh above.<br class=""><br class="">geometry: Shape.brep<br class="">http://forum.freecadweb.org/download/file.php?id=21588<br class=""><br class=""><br class="">kind regards bernd<br class=""><br class=""><br class=""><br class="">_______________________________________________<br class="">gmsh mailing list<br class="">gmsh@onelab.info<br class="">http://onelab.info/mailman/listinfo/gmsh<br class=""></blockquote><br class=""><div class="">-- <br class="">Prof. Christophe Geuzaine<br class="">University of Liege, Electrical Engineering and Computer Science <br class=""><a href="http://www.montefiore.ulg.ac.be/~geuzaine" class="">http://www.montefiore.ulg.ac.be/~geuzaine</a><br class=""><br class="">Tetrahedron V, July 4-5 2016: http://tetrahedron.montefiore.ulg.ac.be<br class="">Free software: http://gmsh.info | http://getdp.info | http://onelab.info<br class=""></div><br class=""></body></html>