<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="">Hello Serban,<div class=""><br class=""></div><div class="">I appreciated your answer very much. First of all, the issues seems not to be related with version 2.9.3 since I tried with 2.8.6 on OS X and Ubuntu as well.</div><div class="">However it worked pretty well with your attached test.geo as well with test_nach_t13.geo, which has been written by myself, strongly influenced by the t13 tutorial you mentioned.</div><div class="">Next I tried to create some boundary layers around the surfaces of the inner cube. Therefore I added </div><div class=""><br class=""></div><div class="">Extrude {0,0,-1} {Surface{3}; Layers{2, 0.001};}</div><div class=""><br class=""></div><div class="">to the code (for creating 2 boundary layers of thickness 0.001 at elementary surface 3). But this only works if I don’t add any Compound or physical surface whatsoever. Please see file test_nach_t13_bound.geo! And I couldn’t adjust the boundary layer height properly, no matter what height I specified in the *.geo file.</div><div class="">I went through the gmsh user guide and tried to find sth. about this topic in the mailing list but didn’t get a clue how this is meant to work. Finally I want to mesh geometry a bit more complicated in a wind tunnel but this is really a long term project. I think first I have to understand the principles of gmsh. And compared to other meshers I find it really hard. No offense, I’m always keen on learning sth. new.</div><div class=""><br class=""></div><div class="">I would be glad for any hint, and thank you very much for your answer!</div><div class=""><br class=""></div><div class="">Best regards,</div><div class=""><br class=""></div><div class="">Kate</div><div class=""><br class=""></div><div class=""></div></body></html>