SimScale CAE Forum

Bad numbered nodes from meshing algorithm


#1

Hi to all,

I am trying to perform Finite Element simulations, including linear static and a non linear static analysis, across two different models. The geometries were meshed using the “Full Automatic Tetrahedralization”, with a second order mesh requested.

After various attempts at solving the problems, ending with errors from the solvers (both Code Aster and Calculix), and getting messages pointing to bad Jacobians, it is obvious that the problem is in the meshes, more specifically, the numbering of nodes.

This could or could not be related with the fact that the meshes are quadratic, but definitely is a problem with the algorithm, in my opinion.

My questions are:

  • Am I right about the cause of the errors?
  • Is it only me that have this problem? Is it a known bug?
  • Is there a workaround besides meshing outside simscale and importing the mesh?

Greetings,


'Propane Tank Burst Analysis' simulation project by ggiraldo
#2

Hi @ggiraldo,

Is this a project that you can share publicly? I have had difficulty with second order meshing in the past, but for me it has been much better the last four or five months.

Christopher


#3

Yeah, off course, you can check my projects, they are the latest two:


#4

Hello @ggiraldo @cjquijano,
the problem is indeed a meshing issue that we are currently trying to fix. If all goes well we will have an improved version of the second order meshing algorithm online next week.

The actual problem does not come from wrong orientations, but from “collapsed” elements, similar to this:

Sometimes when trying to set the middle nodes on the geometry the algorithm merges those together and creates completely flat element domains.

Actually there is no workaround other than waiting for the next release where the situation should be improved.

Best,
Richard


#5

@rszoeke

Hi Richard, now I see.

I will proceed with a linear mesh for the simulation, and will update the project when the fix come alive.

Greetings and thanks for the explanation.


#6

@ggiraldo,

quick heads-up: A fix is implemented and has gone through testing. Will be online soon!

Best,

David


#7

@dheiny

Hi David,

Let me know when it is released, I will test and report back.

Greetings,


#8

@ggiraldo!

Thanks for your deep concern. Highly appreciated! :relaxed: It is already well tested :slight_smile: You have to just start using it :wink:

But still I look forward to your reply. Hopeful to get a positive reply :smile:

Regards,
-Ahmed


#9

@ahmedhussain18

Is it live?


#10

no not yet… But I will keep you updated :relaxed:


#11

Hey @ggiraldo!

I am glad to tell you that the fix is now live. You can now test it :slight_smile:

Best,
-Ahmed


#12

@ahmedhussain18 @dheiny @rszoeke

Hi, I have been trying to test the new meshing, but I get a simulation error, that I think is not related to the mesh.

You can check my test project:

https://www.simscale.com/projects/ggiraldo/cik-fia_kart_chassis/


#13

Hey @ggiraldo!

It’s due to memory allocation problem. It says : Error during the dynamic allocation. It was not possible to allocate a memory zone length 204226624 (bytes). Either choose a bigger machine or reduce your mesh size. I would recommend to do the later one. With second order elements it will be good to go with a normal mesh.

Best,
-Ahmed


#14

Thanks @ahmedhussain18

So the problem was a too big problem, I am meeting the limits!


#15

@ahmedhussain18 @dheiny @rszoeke

So I could finally accomplish the simulation, in my case can say that the problem with the second order mesh is gone.

Greetings to all, and thank you for this great platform!


#16

Hi @ggiraldo,

glad it worked out. Let us know in case you encounter any other issues!

Best,

David