FSAE Meshing Errors/Help!


#1

Hello,

I am trying to make a mesh to perform CFD on an FSAE car. Currently, I get errors saying that the machine runs out of memory, or a solid has an error. The link to the project is: https://www.simscale.com/projects/mmccann/fsae_2017-workshop-s2-full_car_aerodynamics_1/

I am using the geometry “R3 (Trimmed Chassis)” geometry.

Does anyone have any tips or suggestions to solve the mesh?

I have been exporting the assembly out of Solidworks as an IGES file, and then uploading to Simscale.


#2

Hi @mmccann!

Looking at your geometry I would say to first clean it up and make sure it is watertight, has no overlapping surfaces and no other artifacts in it.

Regarding the export data format: “The STL format can only be used for fluid mechanics analysis since only certain meshing algorithms on SimScale support it.” (Doc Source).

All the best!

Jousef


#3

Thank you for responding, @jousefm!

So I would need to fix areas like the side pod hitting the nose cone area? and where the chassis is in the nose cone?
Or is there a way to program the meshing solver to fix some of it?
I was also mistaken in which format I previously used, I started with IGES and the last version I uploaded with a STEP format.


#4

Hi @mmccann!

Unfortunately the Mesh Generator does not fix geometries automatically, this has to be done by the user. Are you able to export your geometry in STL format? You could also try OnShape for that.

Let me know how things go!

Jousef


#5

@Jousefm,

I believe I have cleaned the geometry up enough to work with an automesh, I also reduced the car to a half car model.
Do you have any tips for creating your own mesh?

Thank you!


#6

Hi @mmccann!

Is the link the same or did you create another project for the new model? Just to be sure!

Best,

Jousef


#7

I have added the geometry to the same project, however now I am getting a different error. The mesh will finish, but the simulation will run and then error out. However, the error log says that the job was completed successfully. Have you seen this error before?


#8

Hi @mmccann!

The error probably emerges from the very small bounding box domain you have chosen. Make sure you increase its size! Having a look at some Public Projects and using them as a template can help you here! I am pretty sure once you fix the domain size you will have no problems with the simulation!

Best,

Jousef


#9

Good afternoon @jousefm,

I am assuming that you are talking about the background mesh box that is too small?
What would a good size be for it? (Or a general recommendation?)

I have been using some of this tutorial to help me!


#10

Hi @mmccann!

Exactly! For more detailed information on the bounding box size I am tagging @pfernandez here who has a good amount of knowledge on this. For your application I think 2 lengths upstream, 3-4 lengths downstream and 2-3 times the width in each direction are sufficient.

Cheers!

Jousef


#11

@jousefm

Thank you very much!

I have made a second project file, and seem to have gotten decent results using the automesh feature. The link is below.
https://www.simscale.com/projects/mmccann/full_car_try_1/

Do either of you have any good post processing tips?


#12

Hi @mmccann!

I am wondering what you mean by decent results as the last operation you have started is still with a domain that is way too small :thinking: Am I missing something here?

And before putting to much text about post-processing itself, let me just give you one of many workshops we had related to post-processing procedures with our platform as well as the offline version of Paraview: FSAE 2017. Of course you can find several others in the Workshop & Webinars Section of the forum. Hope that helps!

Cheers!

Jousef


#13

@jousefm, any results are decent to me right now, because I have not been able to have much success in getting a simulation to finish!

What is the benefit of Paraview VS the online post processor?

Have a great day,

Morgan McCann


#14

Great @mmccann!

Feel free to add some nice comments to your project like it has been done here: Project Template.

With the online post-processor you can immediately see your results and make fast adaptions to the simulation parameters if necessary without having to download all of the data written during the simulation to your local machine. On the other hand the offline version offers more customizability and post-processing features in general.

Hope that short outline helps a bit for future simulations here on SimScale :wink:

All the best!

Jousef


#15

Hey @jousefm,

I have ran into a strange issue with my mesh. The mesh completed successfully, however when I go to select it for a simulation it will not let me. How can I fix this?

I get an error message saying “Your changes could not be saved. Please try with different settings or input.
Error code cmqen4iu”

Project: R5+ and No Aero
Geometry: R5 Added Side Skirts
Mesh: R5_SideSkrits_Morgans_Mesh

Thanks!


#16

@jousefm

Sorry for the multiple posts, but when I tried to remake the mesh, it allowed me to select the mesh. However, the simulation failed. I googled the error and the posts I found online about it are telling me the machine is running out of memory. Is there a way to increase the memory available to the machine?

Thanks!


#17

Hi @mmccann!

The only simulation I found with a message was one saying: “The specified maximum runtime of the job was exceeded…”. In order to fix this you have to increase the Maximum Runtime in the Simulation Control as depicted in the picture below.

MaximumRuntime SimScale

Above the marked field you can define the number of cores. Another issue I found: Your fluid domain is way too small in order to get accurate results for your simulation. Please make sure to increase its size!

All the best!

Jousef


#18

Hello @jousefm, The error I was getting is: “mpirun noticed that process rank 11 with PID 162 on node exited on signal 15 (Terminated).”

That was for the simulation “R5_ChangedInterval” under the project “R5+ and NoAero.”
You will notice that I also expended the size of domain in the mesh.

Thanks for your help!


#19

Hi @mmccann!

There seems to be a big issue with your mesh in the first place with almost 80000 illegal cells which is way too much. On top of that the refinements are too high causing the mesh to load for ages. You can easily go down from 23 million to 10 million cells maybe or even less - at the moment it is just an overkill.

I would fix that first, bring down the number of illegal cells and there should be nothing else in the way to get nice results. Let me know if you have any further question.

Best,

Jousef


#20

@jousefm,

How do I lower the illegal cell count?
Decrease the number of cells in each direction?
This mesh is the mesh that the FSAE tutorial showed us how to make.

I really appreciate you helping me out with this! I’m new to CFD and there is a lot to learn. Thank you!