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[Gmsh] Gmsh 3.0 - Boundary layer mesh

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Old   April 14, 2018, 04:55
Default Gmsh 3.0 - Boundary layer mesh
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Paul Bertrand
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Dear all,

First, I already posted this question in another forum ("Mesh Generation and Pre-processing") before to find this forum dedicated to opensource meshers. Please tell me if I have to delete one of these posts...

I just begin to use Gmsh and I have some problems with the last version. I searched some solutions on forums or in the documentation but I still have some problems :

I am trying to use Gmsh to mesh 3D models by taking into account the boundary layer.

My 3D model is from a .STP file and I tried to use the GUI to generate meshes.
I have no problems to generate 3D meshes which are well exported to OpenFoam.

Now, I want ton add some prisms layers at walls to take into account the boundary layer.
I followed all the information that I've found on forums or documentation but it seems that nothing happens when I use
Mesh -> Define -> Size Fields -> New -> Boundary Layer (with the GUI).

I have no errors in the dialog window below, but I have no changes in the mesh...

I think the reason is that I don't fill the fields with good information, especially about EdgesList and NodesList ??
I try to apply layers of prisms on surfaces (as I have a 3D model...) and I am not sure what is expected in these fields (and what is the format (1, 2, ... ?). I have noticed the values of each surface but I don't know how to input them in the fields...

My questions :
- Is there a good tutorial for Gmsh and is there a method described with tutorials or examples about how to do these kinds of meshing or operations ?
- How can I input the expected informations about faces selected, ... in the Boundary Layer window fields (format, ...) ?

Thank you very much in advance for your help and answers,
Best regards,
Paul
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Old   April 17, 2018, 04:30
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Paul Bertrand
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Hello,

It is not the solution that I hoped but I think it's the right solution (?) :
If someone is interested, I will post a more detailled message but I finally used Engrid with a surface mesh from Gmsh (file .msh).
Engrid is very efficient and allows to create a prismatic boundary layer easily, almost as easily as for commercial software.

I will try to improve the method and I will come back to detail it...

But if someone has other method based on Gmsh, I am still interested...
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Old   July 5, 2018, 16:36
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James Wright
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Not to dig up an old thread, but just so anyone knows, gmesh doesn't support 3D boundary layer meshing anymore.


See the revision 2.15.0:

Quote:
2.15.0 (December 4, 2016): .... improved 2D boundary layer field & removed non-functional 3D boundary layer field; ....
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Old   July 10, 2019, 16:26
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G. S.
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Quote:
Originally Posted by PaulBet View Post
Hello,

It is not the solution that I hoped but I think it's the right solution (?) :
If someone is interested, I will post a more detailled message but I finally used Engrid with a surface mesh from Gmsh (file .msh).
Engrid is very efficient and allows to create a prismatic boundary layer easily, almost as easily as for commercial software.

I will try to improve the method and I will come back to detail it...

But if someone has other method based on Gmsh, I am still interested...
Paul, did you come with a procedure for the boundary layer mesh in 3D?

I'm very interested in it, basically an issue I foresee is the use of engrid in a Windows OS machine. I use Openfoam through WSL on Win10 but it seems that it is nearly impossible to install engrid the same way it's done with Openfoam.

Please let me know if you have any extra information on this.

Thanks in advance.
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Old   December 2, 2019, 09:33
Post GMSH 3D Hybrid- Extrusion + Unstructured- Combine or Fuse or Join 3D meshes
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ali ahmed
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cl__1 = 1e+22;

// This Mesh contains a small box inside a outer large box acting as farfield. The surface of small inner box is extruded
// and its required to combine the outer unstructured mesh with the inner extruded mesh on the inner box surfaces, Which command can be used to fuse or combine the mesh //into one mesh
Point(1) = {-100000, -100000, -100000, cl__1};
Point(2) = {-100000, -100000, 100000, cl__1};
Point(3) = {-100000, 100000, -100000, cl__1};
Point(4) = {-100000, 100000, 100000, cl__1};
Point(5) = {100000, -100000, -100000, cl__1};
Point(6) = {100000, -100000, 100000, cl__1};
Point(7) = {100000, 100000, 100000, cl__1};
Point(8) = {100000, 100000, -100000, cl__1};
Point(9) = {0, 0, 0, cl__1};
Point(10) = {0, 0, 10000, cl__1};
Point(11) = {0, 10000, 0, cl__1};
Point(12) = {0, 10000, 10000, cl__1};
Point(13) = {10000, 0, 0, cl__1};
Point(14) = {10000, 0, 10000, cl__1};
Point(15) = {10000, 10000, 10000, cl__1};
Point(16) = {10000, 10000, 0, cl__1};
Line(1) = {1, 2};
Line(2) = {1, 3};
Line(3) = {3, 4};
Line(4) = {2, 4};
Line(5) = {1, 5};
Line(6) = {2, 6};
Line(7) = {5, 6};
Line(8) = {6, 7};
Line(9) = {4, 7};
Line(10) = {3, 8};
Line(11) = {8, 7};
Line(12) = {5, 8};
Line(13) = {9, 10};
Line(14) = {9, 11};
Line(15) = {11, 12};
Line(16) = {10, 12};
Line(17) = {9, 13};
Line(18) = {10, 14};
Line(19) = {13, 14};
Line(20) = {14, 15};
Line(21) = {12, 15};
Line(22) = {11, 16};
Line(23) = {16, 15};
Line(24) = {13, 16};
Line Loop(1) = {-1, -4, 3, 2};
Plane Surface(1) = {1};
Line Loop(2) = {-5, -7, 6, 1};
Plane Surface(2) = {2};
Line Loop(3) = {4, 9, -8, -6};
Plane Surface(3) = {3};
Line Loop(4) = {10, 11, -9, -3};
Plane Surface(4) = {4};
Line Loop(5) = {-2, -10, 12, 5};
Plane Surface(5) = {5};
Line Loop(6) = {7, 8, -11, -12};
Plane Surface(6) = {6};
Line Loop(7) = {13, 16, -15, -14};
Plane Surface(7) = {7};
Line Loop(8) = {17, 19, -18, -13};
Plane Surface(8) = {8};
Line Loop(9) = {-16, -21, 20, 18};
Plane Surface(9) = {9};
Line Loop(10) = {-22, -23, 21, 15};
Plane Surface(10) = {10};
Line Loop(11) = {14, 22, -24, -17};
Plane Surface(11) = {11};
Line Loop(12) = {-19, -20, 23, 24};
Plane Surface(12) = {12};
Surface Loop(1) = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};
Volume(1) = {1};
Physical Volume("box_02") = {1};
Extrude{Surface{9};Surface{10};Surface{12};Surface {7};Surface{8};Surface{11};Layers{{10},{1000}}; Recombine;}
//Extrude{Surface{7};Surface{8};Surface{11};Layers{{ 10},{1000}}; Recombine; }

Transfinite Curve {10, 3, 9, 11, 12, 5, 7, 6, 1, 8, 4} = 10 Using Progression 1;
//+
Transfinite Curve {23, 22, 24, 17, 13, 16, 14, 20, 19, 18, 15, 21} = 10 Using Progression 1;
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