[Gmsh] How can I fix mesh size in GMSH?

nazmulislam · March 15, 2023, 22:14

Hi,

I have constructed geometry for an axisymmetric periodic tube and have made unstructured mesh in GMSH.

However, I am not sure how can I fix the mesh size (what will be mesh size) to get a convergent solution?

I really appreciate your help in this regard.

Hr_kules · March 16, 2023, 07:05

Hi,

what exactly do you mean by fixing?

nazmulislam · March 16, 2023, 07:14

By fixing I meant the mesh size to get the convergent solution.
That is, what mesh size should i consider for the convergent solution.

Hr_kules · March 16, 2023, 07:33

Hi,

There is, to my knowledge, no answer to this but to run multiple simulations with different mesh sizes and see wether the results change with the mesh size or not. (Grind inpedendent solution)
If your mesh already fails to converge changing the mesh size won't magically fix all your problems. Consider the checkMesh utility of openFoam, if this is without errors you still don't have the guarantee that your simulation will converge. Your boundary conditions could be wrong, the solver not suited for your case or the numerical schemes (fvSolution/fvSchemes) could be wrong.

nazmulislam · March 17, 2023, 03:08

Hello,

Thanks for providing your suggestions in this regard.

I am solving unsteady laminar, incompressible flow and I am using icoFoam solver to do this.

Cheers

March 15, 2023, 22:14	How can I fix mesh size in GMSH?	#1
nazmulislam Member Nazmul Islam Join Date: Feb 2023 Posts: 32 Rep Power: 3	Hi, I have constructed geometry for an axisymmetric periodic tube and have made unstructured mesh in GMSH. However, I am not sure how can I fix the mesh size (what will be mesh size) to get a convergent solution? I really appreciate your help in this regard.

March 16, 2023, 07:33		#4
Hr_kules Senior Member Nico Join Date: Jan 2022 Location: Germany Posts: 122 Rep Power: 6	Hi, There is, to my knowledge, no answer to this but to run multiple simulations with different mesh sizes and see wether the results change with the mesh size or not. (Grind inpedendent solution) If your mesh already fails to converge changing the mesh size won't magically fix all your problems. Consider the checkMesh utility of openFoam, if this is without errors you still don't have the guarantee that your simulation will converge. Your boundary conditions could be wrong, the solver not suited for your case or the numerical schemes (fvSolution/fvSchemes) could be wrong. nazmulislam likes this.

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March 16, 2023, 07:05		#2
Hr_kules Senior Member Nico Join Date: Jan 2022 Location: Germany Posts: 122 Rep Power: 6	Hi, what exactly do you mean by fixing?

March 16, 2023, 07:14		#3
nazmulislam Member Nazmul Islam Join Date: Feb 2023 Posts: 32 Rep Power: 3	By fixing I meant the mesh size to get the convergent solution. That is, what mesh size should i consider for the convergent solution.

March 17, 2023, 03:08		#5
nazmulislam Member Nazmul Islam Join Date: Feb 2023 Posts: 32 Rep Power: 3	Hello, Thanks for providing your suggestions in this regard. I am solving unsteady laminar, incompressible flow and I am using icoFoam solver to do this. Cheers