You need to inspect the mesh. If you did, you would see there are holes which indicate issues in the mesh:
This can usually be fixed by adjusting some meshing tolerances. Here is what I did tp get a better mesh:
- Increase the snap tolerance. This helps avoid small cut cells.
- Decrease the intersection and dot product tolerances.
- Increase the wall distance tolerance.
- Increase the domain size in the z-direction.
After that I also changed some numerical setings:
- Set norm_g=0 to relax the convergence criteria.
- Switch to first order discretization scheme.
- Increased max number of iterations for pressure and velocity.
- Increased max velocity factor.
Remember to use the xmin, xmax etc whenever possible when defining regions. You should almost never modify the Background region with hard-coded values, keep the xmin, xmax etc settings so you can change the domain extent without having to manually edit the region.
This runs fine in serial but you should consider running this in parallel (DMP) on a linux cluster.
Please try the attached:
tube-cup-together-flow-only_2025-11-10T082431.311071.zip (940.4 KB)