Is it possible to remesh with gmsh?

Question

I am currently working on remeshers for my simulations (academic purpose) and I try to find a method to remesh previous meshes using Gmsh. The first mesh (normalMesh.msh) was created using a .geo file (normalMesh.geo) and the new meshes should be either coarser or finer depending on the location and stress distribution (Abaqus will be my solver). MWE is given below.

normalMesh.geo

Point(1) = {0, 0, 0, 1.0};
Point(2) = {0, 2, 0, 1.0};
Point(3) = {2, 2, 0, 1.0};
Point(4) = {0, 1, 0, 1.0};
Point(5) = {1, 2, 0, 1.0};
Circle(1) = {1, 2, 3};
Circle(2) = {4, 2, 5};
Line(3) = {5, 3};
Line(4) = {4, 1};
Line Loop(1) = {2, 3, -1, -4};
Plane Surface(1) = {1};
Physical Surface("surf1") = {1};
Physical Line("setTop") = {3};
Physical Line("setBot") = {4};
Physical Line("setInner") = {2};
Physical Line("setOuter") = {1};

If you now mesh the .geo file

gmsh <name_of_your_geo_file.geo> -2 <-o name_of_the_output_file> 

you can view it in gmsh.

If you mesh finerMesh.geo, you will see what I aim to get.

Point(1) = {0, 0, 0, 0.3};
Point(2) = {0, 2, 0, 1.0};
Point(3) = {2, 2, 0, 1.0};
Point(4) = {0, 1, 0, 0.3};
Point(5) = {1, 2, 0, 1.0};
Circle(1) = {1, 2, 3};
Circle(2) = {4, 2, 5};
Line(3) = {5, 3};
Line(4) = {4, 1};
Line Loop(1) = {2, 3, -1, -4};
Plane Surface(1) = {1};
Physical Surface("surf1") = {1};
Physical Line("setTop") = {3};
Physical Line("setBot") = {4};
Physical Line("setInner") = {2};
Physical Line("setOuter") = {1};

If you now compare both .geo files, you will see that I only slightly changed 2 lines. I changed line 1 (from 1.0 to 0.3) and line 4 (from 1.0 to 0.3). I want to be able to only manipulating the .msh files to get the same result or remeshing the .msh files.

I appreciate any kind of suggestions and help coming up.

Answer 1

It is a tricky thing to do (in pure GMSH) by using only the MSH file. Because, conceptually, the MSH file does not contain information about the underlying geometry that was discretized.

However, certain remeshing capabilities are present in GMSH. See tutorial 13 "Remeshing without underlying CAD model" for remeshing of an STL file. For your task, you would have to classify your mesh elements, so that only the ones that need refinement are selected. Then, you would apply a new characteristic length in the right points.

Unfortunately, I was not able to achieve the desired result while quickly trying it; but it is certainly possible with enough efforts.