# [Gmsh] structural mesh in a half ellipse

Zhekai Deng zhekaideng2014 at u.northwestern.edu
Fri Oct 28 02:59:12 CEST 2016

```Hello all,

I am very new to gmsh, and try to use some of the gmsh functionality to
help with my project. I would like to create a structural mesh on a half
ellipse. I have tried to use the transfinite the line, and surface, and
then recombine it. However, the non-orthogonality of the mesh is even
higher than the unstructured triangular mesh, possibly because there is
only very short gap between my boundary, which cause my mesh is very
"skewed".

I have attached my code below, and it is very short.  I wonder does anyone
has some idea on creating structural mesh in this geometry ?  My initial
idea is that have the rectangular mesh all the way down except the bottom
that attach with the ellipse boundary. However, I did not find any
information on how am I able to do that. Any suggestion is appreciated.
Thank you!

lc = 1e-2;
Point(1) = {-1, 0, 0, lc};
Point(2) = {0, 0, 0, lc};
Point(3) = {1, 0, 0, lc};
Point(4) = {0,-0.1,0,lc};
Ellipse(5) = {1,2,2,4};
Ellipse(6) = {4,2,2,3};
Line(7) = {3,2};
Line(8) = {2,1};
Line Loop(9) = {6,7, 8,5};
Transfinite Line "*" = 50;
Plane Surface (11) = {9};
Transfinite Surface "*";
Recombine Surface "*";
Physical Surface("flowing_layer") = {11};
Physical Line("Bottom_Left") = {5};
Physical Line("Bottom_Right") = {6};

Best,

Zhekai
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