[ICEM] Mesh external and internal of sphere, Convert Block Type

hand90 · April 8, 2019, 04:26

Hi everyone

Once more I am interested in meshing a sphere. The main issue I encounter is a mesh conform interface between the external of the sphere and the internal using a hybrid mesh. For the external mesh I found many good videos which helped me to create the mesh with ease (https://www.youtube.com/watch?v=S6R3e4Ac9jY). However to create a good quality mesh on the inside I intend to use a tetra mesh. I have found the option "Convert Block Type" which has allowed me to create a tetra mesh. However when computing the tetra mesh, the mesh does not match the hexa nodes at the sphere surface.
Does anyone know how to get a good interface?

Thank you for helping out.

Gert-Jan · April 9, 2019, 06:56

You will never get a conformal mesh with hex on the outside and tets on the inside. Triangles simply do not match squares. And when converting triangles to squares, then you end up with a unstructured hex mesh in the inside, which will not match your structured mesh on the outside. Also you always end up with some triangles from tets or pyramids.

But if you start blocking from the inside of your sphere and continue with that blocking to the outside, then you end up with a perfect hex mesh, not?
If you don't do that, than probably your sphere is not empty on the inside? Maybe you should explain clearly what you are trying to do, what the goal is, and add a picture.

Alternatively, stop using ICEM and use the Workbench mesher. It can create a unstructured hex (but conformal) mesh for you.

Far · April 13, 2019, 07:10

Quote:

Originally Posted by hand90

Hi everyone

Once more I am interested in meshing a sphere. The main issue I encounter is a mesh conform interface between the external of the sphere and the internal using a hybrid mesh. For the external mesh I found many good videos which helped me to create the mesh with ease (https://www.youtube.com/watch?v=S6R3e4Ac9jY). However to create a good quality mesh on the inside I intend to use a tetra mesh. I have found the option "Convert Block Type" which has allowed me to create a tetra mesh. However when computing the tetra mesh, the mesh does not match the hexa nodes at the sphere surface.
Does anyone know how to get a good interface?

Thank you for helping out.

Inside of sphere is solid?

hand90 · April 13, 2019, 10:01

Thank you for your relay. You are correct by putting another o-grid inside the sphere a well structured mesh can be achieved. This is the solution to my problem and I have realised that after my post.

What I tried to do initially, is to create a tetra mesh on the inside the sphere with pyramids at the boundary to create a conform boundary. However the inside would be a tetra mesh.

The mesh will be used for an airflow around the sphere, looking at the heat transfer within the sphere. So yes the sphere will be a solid.

Far · April 14, 2019, 23:35

In that case you dont need conformal mesh.

Mesh inside sphere and outside sphere separately. Export them and import them Fluent etc. And create interfaces.

Why? Because mesh requirements for the solid body are much lower than fluid domain. Secondly Fluent recommends that create interfaces at the solid-fluid body intersection.

April 8, 2019, 04:26	Mesh external and internal of sphere, Convert Block Type	#1
hand90 Member Thomas Join Date: Nov 2017 Posts: 37 Rep Power: 9	Hi everyone Once more I am interested in meshing a sphere. The main issue I encounter is a mesh conform interface between the external of the sphere and the internal using a hybrid mesh. For the external mesh I found many good videos which helped me to create the mesh with ease (https://www.youtube.com/watch?v=S6R3e4Ac9jY). However to create a good quality mesh on the inside I intend to use a tetra mesh. I have found the option "Convert Block Type" which has allowed me to create a tetra mesh. However when computing the tetra mesh, the mesh does not match the hexa nodes at the sphere surface. Does anyone know how to get a good interface? Thank you for helping out.

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April 9, 2019, 06:56		#2
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,928 Rep Power: 28	You will never get a conformal mesh with hex on the outside and tets on the inside. Triangles simply do not match squares. And when converting triangles to squares, then you end up with a unstructured hex mesh in the inside, which will not match your structured mesh on the outside. Also you always end up with some triangles from tets or pyramids. But if you start blocking from the inside of your sphere and continue with that blocking to the outside, then you end up with a perfect hex mesh, not? If you don't do that, than probably your sphere is not empty on the inside? Maybe you should explain clearly what you are trying to do, what the goal is, and add a picture. Alternatively, stop using ICEM and use the Workbench mesher. It can create a unstructured hex (but conformal) mesh for you.

April 13, 2019, 10:01		#4
hand90 Member Thomas Join Date: Nov 2017 Posts: 37 Rep Power: 9	Thank you for your relay. You are correct by putting another o-grid inside the sphere a well structured mesh can be achieved. This is the solution to my problem and I have realised that after my post. What I tried to do initially, is to create a tetra mesh on the inside the sphere with pyramids at the boundary to create a conform boundary. However the inside would be a tetra mesh. The mesh will be used for an airflow around the sphere, looking at the heat transfer within the sphere. So yes the sphere will be a solid.

April 14, 2019, 23:35		#5
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,558 Blog Entries: 6 Rep Power: 54	In that case you dont need conformal mesh. Mesh inside sphere and outside sphere separately. Export them and import them Fluent etc. And create interfaces. Why? Because mesh requirements for the solid body are much lower than fluid domain. Secondly Fluent recommends that create interfaces at the solid-fluid body intersection.