When I am working on block 21 as shown：
I meet the problem of The Exodus output format cannot output elements of type UNKNOWN_ELEMENT_TYPE.
I try to use the function in cubit: assign element type to blocks, define element type for block 21.
But at the same time, I also encountered the following similar problem：
I’ve tried several other types and none seem to work.
So what I want to ask is what is causing this problem and how can I solve it.
What commands are generated in the command line? You should have something like:
block 21 volume <id list> # the list of volume ids that should be in block 21
block 21 element type tetra
Make sure you create the block prior to setting the element type.
I add the body to block21：
And attach the element type to block21, it is work well:
But when I try to output as .e file, it gives the following error:
I try the command line you gave：
But it’s the same error like this：
Would you make sure that the tetrahedral mesher succeeded for volume? Execute the commands and look at the graphical results. I want you to verify three thrings.
- Verify you are looking at the correct volume.
draw volume 43
- Verify that the tetrahedral mesh was generated correctly.
draw tet in volume 43
- Verify that the block has elements assigned correctly.
draw block 21
About the command that I gave you earlier, it should have been entered as
block 21 volume 43
without the < >. But that is inconsequential at this point. You are creating the block correctly. Let’s verify that the mesh is correct first as described above.
When I type ‘draw tet in volume 43’, it gives an error, it seems that I did not correctly generate tet on volume 43. But on the view this is successful.
Why is this, how can I divide it correctly, can you give me some advice?
The surface triangle mesh was generated correctly. That is what you are seeing here. That is normally what we draw because there are too many 3D nodes and elements to draw and manipulate quickly.
Issue the command
mesh vol 43 and tell me what the output is and what errors you get.
Small inradius of zero mean you have a triangle with zero area. You can examine the quality of the surface mesh by using the options Mesh/Surface/Quality. The options are highlighted in image below. The poor-quality triangles are colored red. Since your case includes a triangle with zero area, it may be difficult or impossible to visualize. The value highlighted in green lists the id of the triangle with the minimum quality value. This could be the “worst” triangle in the mesh.
How do you fix this? The first thing to try is smoothing the existing mesh. The surface smoothing icon is the iron icon next to the quality icon. For the surface id input, I would put “in volume 43”. This will process all the surfaces in volume 43 not all the surfaces in the model.
I would choose the “Mean Ratio” algorithm first. If that doesn’t help significantly, you can try “Condition Number” smoothing. That will likely be slow.
Check the quality after smoothing and see if has changed.
If that doesn’t help, your mesh is likely constrained by the geometry. I created the poor triangles in the example above by creating vertices on the surface that were very close to one another relative to the mesh size. Small curves can constrain the meshing algorithm. Cubit does not automatically smooth over those small curves, because we cannot predict which features are important.
Cubit does have tools to locate potential problems. I like the the geometry Power Tool. You can access this tool as shown in the image below.
- Click on the Power Tools tab at the bottom of the Command Panel.
- Choose the Geoemtry option from the top tab.
- Enter the volume id to analyze, 43.
- Enter a value that you think is “small” for your model. You can try the Auto button to set a small value. I find it sometimes chooses an inaccurate value.
- Analyze the model and note the small surfaces and curves.
You will have to delete the surface mesh on the surfaces that need to be cleaned up and on any surfaces that share a curve. The right click menu offers some options for cleaning up the small features.
If you get to this point and still have issues, contact me again with the details and I can walk you through cleaning up this model.