Hello,

when I want to generate mesh to my model with max edge size 0.10, the programm shut down. Yesterday it rans for 12 hours and no result... why? I have this system in the picture. I want also use customize Decretize.
Everything works, until I click generate mesh, it will not generate it.

So in the picture you can see my steps. First I did max edge size 0.1. Then I click in the tunnel and on the smaller rectangle and discretize to 6400 segments. Now I want to mesh. If I click automatic generation or max edge and tip again 0.1, it will shut down or will work soo lang 12 hours and more maybe ... What did I do wrong?

Thank you for every help.
Rebecka

The mesh size is extremely small, and the mesh generator module (Gmsh) is unable to process it. You can visit https://gmsh.info/ and submit a topic for assistance.

Thank you !

Hello,

I have a question for customized discretize. If I have a rectangle A (50x50) and rectangle B (10x10) and in B is the tunnel.
And I want the A with max edge 1.5 and B with 0.5 for example.
So how do I start?
First discretize the hole model? So max edge Size 1.5
Then customized discretize, Which segments I select? The for sides of B plus the tunnel? Or only the 4 sides? Here I calculate for resctangle 10x10 f?r 0.5 its 400 segements.
Then if I want to generate mesh, I should type again MaxEdge size, so the same 1.5?

So often I get a Error , Error: bad geometry, or the system close.

Best regards
Rebecka

You can specify only one maxSize. I recommend using the auto command, allowing Gmsh to automatically distribute the mesh based on the defined segment discretization size.

Thank you!

Please one important question. I can?t do anything with my codes, all because of the mesh?. I really don?t know how to work with it. If I do a Second rectangle and discre it more fine, it will get bigger if it reach the tunnel. And if I select the tunnel also the segments and discretize the segments, I get a very fine mesh in the middle, which is very good. But then the results are completely wrong. So I learn a very very small mesh is also not good! I thought it will give me better results, but no.. what am I doing wrong? Should be the smaller rectangle bigger?

Unfortunately, I am unable to assist you with this. The level of mesh refinement you are seeking is too fine for the program to handle. I also don?t quite understand why you believe the model is incorrect simply because you used a different mesh size. Mesh size primarily affects accuracy, but it doesn?t change the fundamental behavior of the model.

From my experience in geotechnical engineering, a mid-sized mesh is generally sufficient to achieve reasonable results. Keep in mind that we?re not designing spacecraft?being off by a few millimeters is typically insignificant. In fact, such small variations are often just numerical noise and fall within the range of uncertainty that cannot be captured by field instrumentation.

I have a question in gmsh...

The programm doesnt understand to draw the circle right so outside, then its a tunnel... i dont know what i am doiung wrong.. what should i change?

// 1. Rectangular geometry (model domain)
Point(1) = {-20, -20, 0, 1.0};  // Bottom-left
Point(2) = {20, -20, 0, 1.0};   // Bottom-right
Point(3) = {20, 20, 0, 1.0};    // Top-right
Point(4) = {-20, 20, 0, 1.0};   // Top-left

// 2. Boundary lines for the rectangle
Line(1) = {1, 2};
Line(2) = {2, 3};
Line(3) = {3, 4};
Line(4) = {4, 1};

// 3. Define tunnel opening
Point(5) = {-2.65, -2.875, 0, 0.5}; // Bottom-left edge of the tunnel
Point(6) = {2.65, -2.875, 0, 0.5};  // Bottom-right edge of the tunnel
Point(7) = {-2.65, 0, 0, 0.5};      // Top-left edge of the tunnel
Point( = {2.65, 0, 0, 0.5};       // Top-right edge of the tunnel
Point(9) = {0, 2.875, 0, 0.5};      // Center of the arc

// 4. Lines for the tunnel opening
Line(5) = {5, 6};  // Bottom of the tunnel
Line(6) = {5, 7};  // Left wall
Line(7) = {6, 8};  // Right wall
Circle( = {7, 9, 8}; // Tunnel arc (corrected point order)

// 5. Define surfaces
Line Loop(10) = {1, 2, 3, 4};  // Rectangle boundary
Line Loop(11) = {5, 7, -8, -6};  // Tunnel opening
Plane Surface(12) = {10, 11};  // Surface with tunnel cutout

// 6. Mesh refinement (finer around the tunnel)
Field[1] = Attractor;
Field[1].NodesList = {7, 8, 9};  // Focus on the arc
Field[2] = Threshold;
Field[2].IField = 1;
Field[2].LcMin = 0.1;  // Finest value
Field[2].LcMax = 2.0;  // Coarsest value
Field[2].DistMin = 3.0;
Field[2].DistMax = 10.0;
Background Field = 2;

// 7. Generate mesh
Mesh 2;


Thank you

Please post your question directly in the Gmsh forum.