Project
My project is diverging and I am not to sure why. The point it is diverging at should not be a place of an issue. I have simulated multiple variations of this project and it never diverged in this specific point except for one other time but that time it was because I labeled the end of the wind tunnel as a pressure outlet instead of an inlet. I have checked and this time I did not do that. Also tried to do a particle trace in the post processor after the simulation diverged to see if I could learn anything more but it would not even show the particles (I have done this on other simulations and this has helped me find the issue.).
Any help would be seriously appreciated thanks!!!
I posted about this a few days ago but I have gotten no reply. I also would like to add that I do not think it is an issue with the mesh because whenever I change the mesh it will diverge in different places, but it always will end up diverging. I am trying to get this simulation finished soon because I am under a time constraint so I would really love some help thanks!!!
Link to original post with more information.
Hi @cyrus_costa,
Thanks for posting on the forum.
Divergence can be caused by many factors, as you must be aware. That’s why it’s better to build your CAD model with potential issues already in mind and avoid:
- Tiny gaps
- Small faces
- Sharp corners
In your case, for instance, we can see that the divergence occurred near a tiny gap/sharp corner:
One common approach to model the wheels is to extend them via some sort of “support” that connects them with the floor, as done in this tutorial.
Best,
Igor
I understand this but not long ago I ran a simulation with the exact same parameters on the wheels, actually the mesh was coarser, and it didn’t diverge. Is there an explanation for this??
After seeing that I did another run and refined the wheels mesh however it diverged in completely different spot where the mesh was EXACTLY the same as a run before. I am worried that something else is wrong with my simulation because it keeps failing in places it has never failed before. So even if I keep refining the parts that are failing I am worried that it will just pick a new point to fail it at continuously and I will just waste all of my core hours remeshing and remeshing.
Divergence may take different amounts of iterations to occur in different places.
For instance, the run seems to have diverged somewhat quickly around the wheel while the solution was still somewhat “stable” somewhere else. After improving the mesh around the wheel the simulation may diverge somewhere else.
PS: the narrow gap that originates between the wheel and the floor is well known for causing divergence issues. Of course it’s not guaranteed that it will cause the simulation to fail but it’s fairly likely to.
As the end user, especially if you are already aware of this, it’s highly recommended to make adjustments to the CAD. If you remove the root cause of the issue (which is often dirty CAD), you’re leaving no chance for divergence to happen.
Cheers
This all makes sense however I have run over 30 simulations with the exact same diameter wheels and no refinements in the area yet on this one it diverges. That is why I think there could be another issue with the simulation.
I have again run the simulation. As of 400 iterations it has not seemed like it will diverge yet something is seriously off because nothing is working how it has worked before that is why I am sure that there is something else wrong with the simulation not just the mesh. Here is a link to a previous simulation where everything should be the exact same besides the model. The current simulation is a version that hopes to improve performance however the numbers I am seeing make zero sense.
