[Gmsh] Problem with Boundary Layer meshing

[Nguyen Anh Khoa Doan]

Dear GMSH Users,

I answer my own question and have an additional one.
I looked into the debug file (tato.pos, toto.pos) to search for the reason
behind my problem and what I found was that it's not that there are some
additional cells but rather that there are cells missing in the other parts
of the boundary layer. The tato.pos file is correct while the toto.pos file
produced has some cells removed.
Looking deeper into the source code, I realised that it is due to the call
to the function filterOverlappingElements at line 711 of the meshGFace.cpp.
Can someone tell me what is the purpose of this function ?
Furthermore, I found out that the only other places where it is called is
at line 913 of the meshGRegion.cpp. But there that line is commented.
Is it an oversight and should the call to filterOverlappinElements be also
commented in the meshGFace.cpp file ?

Thank you for any insight you may provide.

Nguyen Anh Khoa DOAN
Last year dual degree student - Université Libre de Bruxelles - SUPAERO
Aerospace Engineering - Major: Propulsion & Complex Systems and Simulation


On Wed, May 21, 2014 at 10:11 AM, Nguyen Anh Khoa Doan <
nguyen.doan at supaero.isae.fr> wrote:

> Hello GMSH users,
>
> I have a problem regarding the use of the BoundaryLayer feature in gmsh
> for a 2D mesh.
> I have tried to create a boundary layer mesh around a square and use the
> FanNodesLists option to get a fan around the corners. However this creates
> additional quad-cells for some parts of the fan and thus, I get triangular
> cells with a really bad aspect ratio just beyond the boundary layer (see
> picture attached). The same problem arises when trying to mesh the Boundary
> Layer around an airfoil at the TE (see picture).
>
> The code for the square:
> // Gmsh project created on Fri May 16 14:29:34 2014
> Point(1) = {-4, -4, 0, 1.0};
> Point(2) = {-4, 4, 0, 1.0};
> Point(3) = {4, 4, 0, 1.0};
> Point(4) = {4, -4, 0, 1.0};
>
> Point(5) = {-1, -1, 0, 0.1};
> Point(6) = {1, -1, 0, 0.1};
> Point(7) = {1, 1, 0, 0.1};
> Point(8) = {-1, 1, 0, 0.1};
>
> Line(1) = {1, 2};
> Line(2) = {2, 3};
> Line(3) = {3, 4};
> Line(4) = {4, 1};
> Line(5) = {5, 6};
> Line(6) = {6, 7};
> Line(7) = {7, 8};
> Line(8) = {8, 5};
> Line Loop(9) = {1, 2, 3, 4};
> Line Loop(10) = {6, 7, 8, 5};
>
> Plane Surface(11) = {9, 10};
>
> Field[1] = BoundaryLayer;
> Field[1].EdgesList = {5,6,7,8};
> //Field[1].NodesList = {5,6,7,8};
> Field[1].FanNodesList = {5,6,7,8};
> Field[1].hfar = 0.05;
> Field[1].hwall_n = 0.001;
> Field[1].hwall_t = 0.003;
> Field[1].ratio = 1.1;
> Field[1].thickness = 0.01;
> Field[1].Quads = 1;
> BoundaryLayer Field = 1;
>
> Any help would be extremely welcome.
>
> Regards,
>
> Nguyen Anh Khoa DOAN
> Last year dual degree student - Université Libre de Bruxelles - SUPAERO
> Aerospace Engineering - Major: Propulsion & Complex Systems and Simulation
>
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