SimScale CAE Forum

"Maximum number of iterations exceeded"


#1

Hello,

currently I’m working on a flow simulation for room ventilation. Everytime I try to start the simulation I get the “Maximum number of iterations exceeded” error.

Some points:

  • mesh seems fine
  • although there I chose a low velocity at the inlets, the velocities are rising up pretty high in some areas.

https://www.simscale.com/projects/KLemke/hot_spots/

Do you have any ideas?


#2

@KLemke,

I have a suspicion - I’ll run a quick test and get back to you.

Best,

David


#3

@KLemke,

the important parameter to change is the relaxation factor for p_rgh - if you put it to 1.0 your simulation will run. We’ve seen many users running into troubles with this parameter and we’re planning on some changes to make this less error prone.

In addition, I’d recommend some more changes for speed + efficiency - change the linear system solvers to the following:

Last but not least, you’re running a steady state analysis with 4m cells but you want to write out 5 steps, which will give you quite some result data, where most of it is not really interesting, is it? So I’d recommend only writing out the last time step but running more iterations. I ran your 200 iterations, but the solution is not yet converged - so 1000 seems a good next try.

Best,

David


#4

Thank you very much!


#5

You’re welcome! What’s the simulation about? Looks interesting!


#6

It’s about a compressor test rig which will be applied with hot pressure air. The plan is to air-condition the room just with ventilation.


#7

Glad i found this thread.
I was experiencing similar issues with a model that has local relatively high velocities. It also kept exceeding max. iterations. Tried a dozen times to get it to work with no succes. I was blaming my mesh however now i will definitely try this solution.


#8

@STR,

let me know if it does work with changing this relaxation factor! With the next release more robustness improvements as well as new models to simulate buoyant flows will be deployed which shall make the setup easier.

Best,

David