> On 19 Jun 2020, at 09:17, Diogo Nunes <[email protected]> wrote: > > Hello gmsh Users, > > This is a question about modelling 2D surfaces with arbitrary shapes and > sharp angles within the geometry. > The mesh is then used by a radiation-diffraction solver to obtain the > hydrodynamic potential. > It is a specific application to a ship hull but must be similar to many other > applications. > > So we are using gmsh to create a 2D structured mesh of a ship hull with a > geometry looking like the one below (note the appendage in red): > <image002.png><image004.png><image005.png> > > Meshing the overall hull shape has been fairly straightforward and gmsh did > exactly what we expected, yielding a good quality mesh with minimal efforts. > We created my 3 and 4 edges surfaces from lines and B-Splines curves. For > each surface, we defined Transfinite Curves, Surfaces and Recombined each > surface them to get the 2D Structured Mesh: > <image006.jpg> > > The issue is related to the appendage on the stern of the hull (called > “skeg”) as shown on the first picture. If we include this as the same surface > as the hull, the sharp angle would never be captured by the B-spline. > > So far we have tried a couple of things based on processes commonly applied > in other packages: > First we have made a contour of the skeg using B-splines and lines (Line 16, > Line 17, Line 18, Nurb 12, Nurb 13) and split the forward B-spline into 2 > (Nurb 7 and Nurb 8) as shown below. > <image007.jpg> > This has either resulted in endless loops of “Warning: Wrong control point > index in bspline” or in meshing errors in the appendage and surrounding > regions. > > Next we have tried to approximate the contour of the skeg with Nurb 17 to > generate Surface 2 (made of Nurbs 7,8,5,17) and then add 3 separate lines to > produce the side surface of the skeg (Surface 5 made of Nurb 14, 15 and Line > 16) > <image008.jpg> > This resulted in an error message and the Surface 5 meshed with 1 element > only as shown above. > > Have you got any suggestion on how one should proceed to get a 2D structured > mesh of such a geometry with sharp angles (here, the hull and the skeg) and > capture those discontinuities within the mesh, as depicted in the first > figure? >
Can you share a script? It should be doable of all surfaces have 3 or 4 sides. Christophe > > Many thanks, > Diogo Nunes. > > _______________________________________________ > gmsh mailing list > [email protected] > http://onelab.info/mailman/listinfo/gmsh — Prof. Christophe Geuzaine University of Liege, Electrical Engineering and Computer Science http://www.montefiore.ulg.ac.be/~geuzaine _______________________________________________ gmsh mailing list [email protected] http://onelab.info/mailman/listinfo/gmsh
