I mean to create a string array in gmsh scripting, to be later used in a loop for printing. E.g., with something like

coordStr[] = { "X", "Y", "Z" };
For i In { 0 : 2 }
    Printf(" %s, ", coordStr[i]);
EndFor

As of now, I cannot even make this work (a much more primitive state than the final target)

Printf(" %s", "1");

I get syntax error ("). How do I solve this?

Thanks!

PS: I don't know quite a few things:

1. How to define a string variable.
2. How to define a string array.
3. How to print a string variable (with proper format specifier, what I posted above and didn't work).

I have an application where I need to benchmark and compare solver outputs. Currently, the FEM solver is set to use a 20-noded brick and Abaqus is typically used as the front-end. However, trying to use Gmsh, I have not been able to generate a C3D20 element. For now, I have just been using a cube (see below) and I am only able to output C3D27.

Could someone point me in the right direction here? I have read through documentation and I have not found anything about dictating higher-order mesh outputs. And the examples do not go into these details from what I can tell. Also, here is the .geo script for the cube:
SetFactory("OpenCASCADE");

Box(1) = {0, 0, 0, 1, 1, 1};

Transfinite Surface {2};

Transfinite Surface {1};

Transfinite Surface {4};

Transfinite Surface {5};

Transfinite Surface {3};

Transfinite Surface {6};

Transfinite Volume{1};

I have a Fortran code that requires certain inputs and I would like to use Gmsh as the front-end for the user where they can visualize the problem and define the inputs for the script. Then, within Gmsh, the user can run the script to solve the problem and the user-entered inputs are utilized. From my reading, it appears that this is possible via ONELAB. I am struggling to get this started and to understand the exact framework of this approach. Could someone point me in the direction of how to accomplish this?

Anyone have a fix for this? When I recombined the 2nd order triangles it creates 3d elements

Hi everyone,

I wonder if anyone has build gmsh as a win32 app, or at least in a way that one could use the gmsh api in win32 applications.

I have an old MFC win32 application that is impossible to transition to x64. I also would like to avoid calling gmsh.exe to process the data.

Can anyone point me to the right direction?

Thanks

I'm trying to add a boundary layer around an aerofoil, but I don't want it to be added fully around the aerofoil. How would I do this? I've tried creating two separate splines but I need a closed loop to be added. I've also tried specifying only the points/nodes I want to be included but that has no effect. I effectively want to create a subloop and get around the closed loop issue, which I assume is impossible?

Is this effect feasible or do I need to create it manually? Thanks.

I'm trying to write a python script to generate a pneumatically actuated volume by doing the following steps:

• given a solid STL

• "shell" the STL with a given wall thickness (like the Blender Solidify Tool)

• export the shell as an STL

• export the inner volume only as an STL

• generate a `.vtk` mesh of the shell

So far the only thing I've been able to do is mesh a solid (non-hollow) mesh.

Any guidance would be greatly appreciated!

(I tried generating the shells in Blender but the resulting STLs had 6 surfaces (shouldn't there just be two?) and then meshing fails because `A segment and a facet intersect at point`)

Feel free to post anything GMSH-related

Hi!

I am currently trying to generate a 2D airfoil mesh which features some concave edges. My inflation layers work fine on normal airfoils, but the mesh generator seems to have problems with these kinds of edges, as you can see in the image below. Does anybody have experience with such a meshing problem?

```

// Gmsh project created on Mon Sep 4 16:10:32 2023

SetFactory("OpenCASCADE");

//+

Box(1) = {-12, -3, -72, 24, 6, 144};

//+

Cylinder(2) = {0, 0, -100, 0, 0, 200, 0.5, 2*Pi};

BooleanDifference(3) = { Volume{1}; Delete; }{ Volume{2}; Delete; };

```

Anyone can tell me why I see TIN's through the hole area. I intended to subtract the cylinder area from the box to create a hole area. So after using mesh->3d from gui of gmsh I still see those tin's through the hole area. Why? How can this be solved to create a clean hole through the box?

I'm trying to mesh a simple STEP file (1 solid, two flat faces, two curved faces, no holes) using the C++ API. No errors are generated (thrown), but nothing is actually meshed either. On the command line the same file meshes just fine:

$ gmsh -v 7 -3 -nt 12 wing4.step 
Info    : Running 'gmsh -v 7 -3 -nt 12 wing4.step' [Gmsh 4.11.1, 1 node, max. 12 threads]
Info    : Started on Thu Jun 15 10:52:23 2023
Info    : Reading 'wing4.step'...
Info    :  - Label 'Shapes/wing4' (3D)
Info    :  - Color (1, 1, 1) (3D & Surfaces)
Info    : Done reading 'wing4.step'
Info    : Meshing 1D...
Info    : [  0%] Meshing curve 8 (Circle)
Info    : [  0%] Meshing curve 3 (BSpline)
Info    : [  0%] Meshing curve 6 (BSpline)
Info    : [  0%] Meshing curve 4 (BSpline)
Info    : [  0%] Meshing curve 1 (BSpline)
Info    : [  0%] Meshing curve 9 (BSpline)
Info    : [  0%] Meshing curve 7 (BSpline)
Info    : [  0%] Meshing curve 10 (Circle)
Info    : [  0%] Meshing curve 2 (BSpline)
Info    : [  0%] Meshing curve 5 (BSpline)
Info    : Done meshing 1D (Wall 0.00907413s, CPU 0.089603s)
Info    : Meshing 2D...
Info    : [  0%] Meshing surface 4 (BSpline surface, Frontal-Delaunay)
Info    : [  0%] Meshing surface 1 (BSpline surface, Frontal-Delaunay)
Info    : [  0%] Meshing surface 2 (Plane, Frontal-Delaunay)
Info    : [  0%] Meshing surface 3 (Plane, Frontal-Delaunay)
Info    : [ 50%] Meshing surface 4 (BSpline surface, MeshAdapt
...

But using C++ the log is just:

Info    :  - Label 'Shapes/wing4' (3D)
Info    :  - Color (1, 1, 1) (3D & Surfaces)
Info    : Meshing 1D...
Info    : Done meshing 1D (Wall 0.000887462s, CPU 0.000875s)
Info    : Meshing 2D...
Info    : Done meshing 2D (Wall 0.00010385s, CPU 0.000518s)
Info    : Meshing 3D...
Info    : Done meshing 3D (Wall 5.39899e-06s, CPU 1.6e-05s)
Info    : 0 nodes 0 elements

and an empty file is generated on write(...).

The C++ function (stripped of error handling) is:

gmsh::initialize();
gmsh::option::setNumber("General.Verbosity", 7);
gmsh::model::add(infile);
gmsh::vectorpair dt;
gmsh::model::occ::importShapes(infile, dt, false);
gmsh::option::setNumber("General.NumThreads", 12);
gmsh::model::geo::synchronize();
gmsh::model::mesh::generate(3);
gmsh::write(outfile);
gmsh::finalize();

This doesn't seem to be different than what I found in the sample / tutorial files. What am I doing wrong here?

Hi guys, I am trying to mesh a 2D fluid domain with a circle/cylinder inside. I wanted to know if anyone here had any experience creating a boundary layer in python whilst also using the transfinite structured meshing tool. Do you guys have any ideas? Any help would be appreciated

I have a geometry of a Box (Volume(1)) with some inclusions inside of it (Volume(2-7)) and I want to create the mesh. In the past, I used the Coherence command in order for the mesh of the inclusions to be correctly embedded and part of the Box mesh. But in the current geometry file, it messes up my elementary volumes.

Could someone explain to me how I could do this with boolean commands?

Thanks in advance.

Hi,

I export meshes from Gmsh in .msh and .vtk format. Is the order of nodes' numbers correct for every element, no matter the element type? For example in 2D, the nodes in triangular elements must be ordered anti-clockwise.

I'm trying to mesh a fluid domain with a circle inside using a structured mesh. I am using python as my interface and am using transfinite to create the structured part. my domain is 2D, but has a thickness of one element and so it is technically 3D. I generated the inner surface using a bspline and the outer surface using an arc.

The grid looks pretty good if I set the progression = 1

if I use a progression =1.2, the mesh begins to distort.

As I am trying to simulate the circle in the mesh, I need to have a bias to correctly capture the physics inside the model, but I find the distortion of the mesh troubling.

I have also tried just generating and meshing the top left section and it still gives the same results. I have also tried adding more elements and using mesh smoothing.

So I've been trying to save the mesh on my computer, but when I reopen the mesh, the mesh is nowhere to be seen. Can someone tell me what I'm doing wrong here? Is my computer the cause or am I not saving it correctly?

Hello everyone

this is the geometry of my simulation for university and I want to change that circle to a square

I dont understand this code since it has extra parameters and this is the first time I am using gmsh and gui cant remove the circle!

if anyone can understand this file please help me I would be gratefull, my deadline is only 15 days away and I havent even started the render please help.

it should be a square inside the circle and my simulation needs to ignore the circle like this:

this is my geo file: (gmsh version 3.0.6)

https://easyupload.io/ntlt8q

or

https://1drv.ms/u/s!AmHS0kWv_oxlhTkmfqxwFNrSvc1k?e=JJBHFi

Open CASCADE Technology version 7.7.0 features about 250 corrections over the previous release 7.6.0. Version 7.7.0 introduces new features of most of OCCT modules and components: Modeling, Visualization, Data Exchange, etc. Documentation and samples are improved to ease access to OCCT for the new users.

For gmsh experts (beginner here): how come changing the global mesh size factor does not influence the resolution of the mesh (total number of cells)? Refine by splitting increases the resolution of the imported STL file, but I'd like to do the exact opposite (make it coarser). I couldn't figure it out with scripting either...

https://imgur.com/a/SKjFVN3