Number of iterations exceeding


I am new to Simscale and have only really done the compressible golf ball simulation. I used the guide to try simulate a 9x19 mm Parabellum (which I built in freecad and exported as an .stl file) with a muzzle velocity of 460 m/s. I am trying to test whether or not turbulators like the dimples on a golf ball, actually reduce the drag coefficient on things like a bullet or a car (my next model) for my high school thesis. This is then the base model of the 9 mm, which I will compare to the half dimpled one.

Simscale link: SimScale (Tried to attach Freecad file, but Simscale does not accept the format).

Error log:
Maximum number of iterations exceeded when calculating temperature from a thermodynamic potential. This may be caused by low-quality mesh producing unrealistic pressure in a few cells or inappropriate boundary conditions, fluid properties or time step. Inspect fields for large values in the last time step.

At this point I have tried multiple times with different projects, yet I still get the same error. I have read the article that is recommended (and several forum-posts), and found that my meshes non-orthogonality is really high, its max being 73. But I have no idea how to decrease it (I found a really long and complicated forum post, but I am too much of a beginner to even understand what to do, Reducing Non-Orthogonality through CAD & Mesh settings with help from the Mesh Quality Feature), or if it really is the problem? I would be very thankful if someone could help tell me what is wrong with this project.

Hey @Tex03 welcome to the forum!

Looking at the server log it seems this the problem

I am however not at all experienced with compressible simulations but i can make some other universal recommendations for your meshing.

  1. I would look into and change your boundary layer settings. You need to find the correct Y+ value so that you get accurate results. The current settings you have are more of a standard and you will be measuring in the log-law region. You need to be measuring the viscous sub-layer. this means a Y+ of less then 1.

  2. I would also recommend increasing the boundary box layer in front of and to the side of the bullet so you dont have and problems with being too close to a wall

  3. You could also put a finer mesh surface on the bullet itself. What you have will work but if you want to compare to a dimpled bullet. It would be better to have a similar mesh size for both runs and the dimples will definitely require a finer mesh to accurately describe the geometry. I would use a local surface refinement to do this.

Good luck,


Thank you so much Dan for your reply! I will definently look into it, and hopefully I will be able to fix this using your tips.

Compressible flow simulations (Mach > 0.5) are not trivial. I am not fully experienced in those, in addition to @dschroeder suggestions, I would add the following:

  1. The domain is very small compared to the bullet. If you are restricting values in those boundaries, it may generate conflict (strong oscillations → divergence) with the solution inside the domain.
  2. Start with a lower velocity and see how the case works.
  3. Check out this post Post. Again, such solutions easily diverge.

Dan, thank you so much for your response! I’ll look into it, and hopefully, with your assistance, I’ll be able to resolve the problem.