gmsh .m files, reading boundaries

Is it possible to export the boundary information when exporting gmsh mesh. I want to apply forces to certain boundaries in the mesh. I read that one can identify domains in the mesh, but could not find any information regarding boundaries.

Answer 1

[Jaynik]

Hi Divyaprakash,

Assuming the variable 'msh' contains the mesh information from the Gmsh '.m' file. You can read the following answer to read the file in MATLAB: https://www.mathworks.com/matlabcentral/answers/483115-reading-msh-files-3d-in-matlab.

Once you have loaded the mesh information, you can use the findElements function to find mesh elements belonging to a specific region and the findNodes function to find the nodes that belong to a specific region from the Partial Differential Equation Toolbox.

You can directly use the properties of the 'msh' variable to create a triangulation object and use the freeBoundary function to find the outer surface of the mesh. Following is the code for the same:

nodes = msh.POS';  % Node coordinates
elements = msh.TETS(:, 1:4);  % Element connectivity

T = triangulation(elements, nodes);
boundary_faces = freeBoundary(T);

Refer to the following documentation for more details about each function:

• findElements: https://www.mathworks.com/help/pde/ug/pde.femesh.findelements.html
• findNodes: https://www.mathworks.com/help/pde/ug/pde.femesh.findnodes.html
• triangulation: https://www.mathworks.com/help/matlab/ref/triangulation.html
• freeBoundary: https://www.mathworks.com/help/matlab/ref/triangulation.freeboundary.html

For a more detailed solution, it would be beneficial if you could provide additional details about your model.

[Divyaprakash]

Thank you so much!