Two phase flow problem (long pipe) air/water - CFD Expert Help Please

I am trying to learn Simscale to a deeper level. I have completed several models using two phase flow (mostly the tutorial problems). Now I created a model of a problem that I have sorted out in the real world to see if I could model it and come up with the same answer.

Short version is: a diversion pipe, large diameter, transitions from horizontal to 15% slope. In the process it entrains air in a specific flow range. The air causes flow restrictions further down the pipeline. Question to be answered is how much air needs to be vented at air release valves?

Problem: I can’t get the model to run, always getting an error “signal 8 encountered”. I have tried checking things and making adjustments, but just can’t figure out the problem. Maybe it is just too large?

Project Link

I could really use some input from someone with two phase flow experience.

Thanks in advance,

Hey Stephan!

That could be related to the mesh quality, have you checked that already and (if I am correct with the assumption) made some changes to it accordingly? If I missed something related to the setup here, @cfd_squad feel free to jump in :slight_smile:

All the best!


Yes, thanks - I was concerned about that and tried a new mesh with no luck. This afternoon I deleted the model and I am trying to simplify it in Fusion 360 before I import a new one and try a new mesh. Will report here when I know more.


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