3D mesh on slightly concave surface
I have been struggling to create a good 3D mesh around a thin curved surface. Because it is thin, I need to create transfinite surface mesh so that points are located at almost the same location on both sides of the surface. Otherwise, 3D meshes on opposite side of surface intersect and a simulation cannot be run. If I do that on slightly concave part of the surface, Gmsh sometimes connects apexes of adjacent triangles to create a tetra and that creates almost a flat tetra. So far, use of "Alternate" option for surface transfinite mesh and Netgen optimizer have improved the mesh quality, but there are still some low quality tetras remaining. Is there any way to avoid this behavior, or is this a bug?
I'm attaching a simplified sample files. testmesh3.geo
Thank you for your help in advance!