SimScale CAE Forum

How do you view mesh quality?


#1

I’m getting this error: Non-positive jacobian. Degenerated/distorted elements or bad face orientation in the mesh.
Apparently the mesh is not nice so I want to look at the mesh quality and then add some refinements, but I can’t find how to do that. Can anyone help me out? Much appreciated!


#2

Hi @wvisser,

Could you first share your project so that we can have a look at it?

Best,

Jousef


#3

The project is here:
https://www.simscale.com/workbench?publiclink=21c24fc5-ca9e-4163-9b1e-e09533e1e3fe

You can find the error by going to Simulation designer and selecting the to-92-heatsink simulation, where both runs failed.


#4

Hi @wvisser,

can you somehow modify the geometry trying to avoid the issue as depicted in the picture:

This holds for both components inside your mesh. Please get rid of this and re-mesh your geometry.

Usually this fixes the problem. If not, please contact me again.

Good luck!

Jousef


#5

Thanks for the speedy response! I don’t really grasp yet what the issue is. The top of the semi-round part is red but I don’t know what that means and what I can do about it.
I have an additional question (which was my original question), is there a way for me to view the red parts of the mesh like what you’re doing right now?


#6

My pleasure @wvisser.

Could you just delete one “layer” of your two components. That is what I meant.

Can you send me your original model via Email? Contact me privately if you like.

Regarding your question there are several approaches:

  • You can navigate through the right tree. By clicking on the eye symbol you can hide components.

  • The other way is to click on the component(s) and right-click selecting Isolate selection

  • You can also work with the Invert Selection mode which is quite useful in some cases

Does that somehow covers your question? Maybe I did not get you here.

Make sure you do not forget to send me your CAD model via Email. I will have a look at it and try to mesh it properly.

Cheers,

Jousef


#7

I don’t know what a ‘layer’ is, could you explain that to me? Also, what exactly about these selected parts seems to be the problem? And I thought the red part was some feature to find low quality mesh parts, but it is just a selection, my bad.
The model is here: the ‘to-92-heatsink’ tab, which is the assembly containing 3 parts:
https://cad.onshape.com/documents/bcff6688747c08f61c10883e/w/95c305743302c48430b03c50/e/96cf4a2105b9bfaf88b18027
Again, thanks for the help!


#8

Hi @wvisser!

Ah alright, I see. No - sorry if that somehow gave you the illusion that there would be a hidden option.

Thank you very much for your model. As I saw your “Block” already contains the transistor as well as the heatsink. What I have done now is:

  1. Export only the block as an IGES file

  2. Import into your workbench by selecting the file from your computer

  3. Mesh the geometry

That should help getting rid of the non-positive Jacobian caused by zero or negative volume.

Please keep me up-to-date if that fixes your problems. If so, please also adapt the other models you have.

Good luck!

Jousef