Grid Generation - GMSH - 7 - Controlling Grid Point Density with Fields

GMSH tutorial on controlling grid point density with a combination of field functions.
Tutorials of the GMSH Computational Grid Generation System. A three-dimensional finite element mesh generator with built-in pre- and post-processing facilities
GMSH - gmsh.info/
Tutorials have a focus on creating simple meshes for unstructured Computational Fluid Dynamic Solvers
Prof. S. A. E. Miller, Ph.D.
faculty.eng.uf...
saemiller.com
/ saemiller
mae.ufl.edu/
The University of Florida
Department of Mechanical and Aerospace Engineering
Theoretical Fluid Dynamics and Turbulence Group

[@fountaingoat6802]

Thank you for these GMSH tutorials. They really helped me

[@SAEMiller]

You're very welcome!

[@icojb25]

likewise, thanks very much

[@liboyan7010]

@@SAEMiller Prof. Miller, thanks a lot for these GMSH tutorials!!!

[@VaShthestampede2]

Great video!

[@yagizkaplann]

Does anyone know how to create inflation layer near cylinder surface in this program? What's the tool?

[@terrencepereira169]

Thanks for the trick on how to use 2 box fields

[@arijitsaha1472]

Thanks a lot for this demanding tutorial video. I was wondering if it is possible to use two box fields for background meshing at the same time or not?

[@MdJaforDewan-qq2jm]

I generated a domain of cubic box with inlet and outlet cylinder, Now I want refine the the inlet and outlet cylinder at time with different refinement factor. I used the size field option for this purpose but I can't refine the 2 cylinder at time. When one is refined other is not. Could you please tell me how can I solve this problem?

[@narayanguragain9980]

Hi, I want to know what units gmsh uses while making the geometry. I made the geometry but I'm confused about giving initial conditions due to the units?

[@SAEMiller]

They are just values to my understanding. If you load your grid with a solver, you could assign them then. E.g. if I have 1.5, I could say it is 1.5 m or 1.5 in, in the solver.

[@APiccolo]

Legend!

[@Jonathan-qn3mv]

Thank you for these really helpful videos!
May I know how to mesh a 2D domain that has complex intersecting line segments in it (i.e., a domain including random discrete fracture network)?

[@paulwary]

What exactly is the 1D button, and why do you always click it before 2D? Edit: I think I get it now, it sets up the grid on the boundary of the surface.

[@SAEMiller]

The operation by clicking 1D creates points along the lines or curves (1D). One usually has to discretize lines. The lines form a surface, which is then discretized. Finally, the volume is defined by the surfaces. Each one is discretized in order.

[@paulwary]

@@SAEMiller Thanks. So, shouldn’t 2d call upon 1d implicitly, without you having to push the button? At worst you might lose a little time recomputing the same points

[@JazminZenteno1]

do you use this with nek5000? because it doesn't read it for me :(

[@SAEMiller]

I do not personally but have coworkers who do. I would suggest looking at the output format from GMSH in a text editor and comparing it to the read commands in your source of NEK5000. Then you can match them. Also, suggest looking at documentation if you can't access source code.
Also, I like your music videos on your channel. That is wonderful!

[@GauravGupta-by1ml]

Nek5000 requires hexahedral mesh in the GMSH format.

[@piersonguthrey216]

How would I add a mesh to inside the circle while still maintaining that shape? I want a mesh that will resolve that circular shape within the larger domain.

[@SAEMiller]

If I understand your question - one would create a second domain (surface mesh) inside the circle.

[@charithjeewantha]

Thank you for these playlists. May I know how to avoid the grid generation inside the circle. When I try to have this diagram, it also creates a grid inside the circle....

[@SAEMiller]

I think that it is likely that you have not cut a hole (so to speak) from your geometry.

[@charithjeewantha]

@@SAEMiller thank you for the response. May I please know from where I can cut a hole. I tried various surface options but couldn't figure out the correct method. It there a direct command we can select from the left hand side menue?

[@moshehollander9608]

Excellent video! Any chance you could walk through the process of applying the 'BoundaryLayer' size field? I have been trying to do so with little success. For some context, I'm trying to create a boundary layer around an airfoil shape.

[@SAEMiller]

At the time of making this video I believe that the GMSH team temporarily disabled that feature. I'm not sure why. You can do it manually by making a transfinite mesh. Though this will not be structured. Alternatively, you can in the mesh options turn on growth and this will grow a boundary in 2D. I do not believe that this is working in 3D. Please correct me if I'm mistaken.

[@moshehollander9608]

@@SAEMiller Thanks for the quick reply! That is indeed very odd, especially given that it still seems to appear as an option in the GUI menu... I'll give your suggestions a try.