[Gmsh] Mesh and geometry edges do not coincide: flow over cylinder

[Christophe Geuzaine]

> On 4 Aug 2018, at 23:23, Deep Bandivadekar <deep.bandivadekar at strath.ac.uk> wrote:
> 
> Hello,
> 
> Attached is a simple script for a fully structured "flow over cylinder" geometry. If we zoom in to the cylinder wall region, the mesh lines do not seem to coincide with the actual geometry. Why does it happen? How do I avoid this? The circles also look a bit jagged (as if a polygon) rather than smooth.

The discrepancy is only in the graphical representation: OpenGL cannot render curves - so curves have to be subdivided into straight line segments.

You can increase the number of sub-segments for the graphical representation with the "Geometry.NumSubEdges" option (in the GUI : Tools->Options->Geometry->Aspect->Curve subdivisions).

> 
> I did have a smooth nice mesh earlier but I reduced the overall dimensions a bit and this happened and now it won't go back to the same even if I use the original script. Meshed geometry with well conforming edges: https://drive.google.com/open?id=1tMSst0q8pRpWlJGP6KAj3pMzlnix9QR- (.msh file 57mb)
> 
> Can you please tell me where is the problem?
> 
> Thanks
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— 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine

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