[Gmsh] Transfinite Surface with OpenCASCADE engine

[Christophe Geuzaine]

Dear Marco,

In your geometry OpenCASCADE generates a degenerated curve (curve 6), which the transfinite meshing algorithm could not handle.

The latest development snapshot now simply ignores such degenerate curves in the transfinite algorithm, which seems to fix the issue.

Christophe


 
> On 6 Jul 2019, at 18:29, Marco Fossati <marco.fossati at strath.ac.uk> wrote:
> 
> 
> Dear Prof. Geuzaine,
> 
> I would like to kind ask for support in solving an issue with gmsh with which I have been struggling from many days now.
> 
> I am using the OCC engine: I need it since I must use the boolean operation to create the root of the biconvex wing along the cylindrical fuselage. (Incidentally I tried another option with the Built In engine + surface filling but I was not getting a curvature that was smoothly connecting with the rest of the surface but was “bulging” out).
> 
> I have vehicle with an ogive at the nose. This ogive is created by extruding by revolution around its longitudinal axis. While trying to create a transfinite recombined mesh over it I get the error message:
> 
> .Error   : Surface 1 is transfinite but has 1 holes
> 
> If I extrude the line to create the ogive by asking to extrude the mesh, I get a structured mesh in the ogive, but this prevents me to apply the transfinite on the cylindrical surface adjacent to the ogive.
> 
> Please note that I need to create a manual boundary layer from the surface so I would need to have transfinite recombined. I tried with extruding the surface mesh along the normals to create a boundary layer with prisms but this creates conflicts of advancing fronts at the intersection between the wing and the fuselage (in the part after the ogive) and does not give me enough points in the viscous layer.
> 
> I am attaching my geo file for clarity.
> 
> Looking forward to a kind response.
> Many thanks for your help and support
> 
> Best regards
> Marco
> 
> 
> _____________________________________________________________________
> Marco Fossati, PhD, FHEA, CEng
> Lecturer in Computational Aerodynamics
> 
> Laboratory for Future Air-Space Transportation Technology
> Aerospace Centre of Excellence<https://www.strath.ac.uk/engineering/mechanicalaerospaceengineering/aerospacecentreofexcellence/>
> 
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— 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine