[Gmsh] Mapping of Unstructured Grid on Similar Patches

Sachchit Vekaria sachchit at iitgn.ac.in
Tue Apr 7 16:48:43 CEST 2015


Hi,

First of all I want to thank for making the wonderful software like gmsh
open source.

I am using it for CFD mesh generation. As far as inviscid flows are
concerned gmsh is best software I came across. Same goes when using it for
structured grid. But when I want to use it for viscous flows using hybrid
grid (prism layer) I am not able to figure out the best method.
I will try to explain the problem using the geometry shown in attachment_1.

I have tried the following command,
tmp[] = Extrude {
  Surface{1:6:1}; Layers{7, 3}; Recombine;
};
but it is not good for geometry with acute angles. Attachment_2 shows the
problem.
So I tried using creating a approximate box around the geometry, which is
of almost same shape as the geometry. Then I defined the faces made by line
joining the main geometry and outside box as transfinite (also recombined).
Attachment_3 explains what I mean.
But I am not able to generate mesh, when both geometry and box is
unstructured. I believe the reason is that both grids are not similar.

The only working way I am able to do is to making it completely transfinite
as shown in the Attachment_4. But the problem is when using this algorithm
for three side surface there are very poor quality cells near one of the
corner. And even worse part is that quality will go further down in
unstructured grid just nearby this cells when joining the transfinite to
unstructured Domain.

If there is a way to map the unstructured grid kindly let me know. Also if
there is other simpler way to generate prism layer kindly let me know.

If there is no way to do that is there any other software which can help? I
have tried few of them but the kind of control and parametrization gmsh
allow is unparalleled.

Thanks,
-- 
Sachchit Vekaria,
Senior Undergraduate,
Mechanical Engg.,
IIT Gandhinagar,
Contact No : +919429950476
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