Negative Volumes Created After Run Start
 

Hi guys.

I'm trying to run a steady state simulation. Before running the simulation, mesh diagnostics tells me that I have no negative volume cells, but after starting the simulation I get a report that I have 2 negative volume cells, and to repair the mesh before proceeding.

What is likely causing this, and how can I repair/avoid it?

I run into this occasionally. It's hard to say what causes it other than an error in the meshing process. Perhaps someone else can weigh in on that, however.... You can try to avoid it by changing your mesh parameters in areas near to the zero volume cells (size, target value, min value). Or you can try meshing with a different number of cores (one more or less than what you are using now, assuming you are meshing in parallel.)

However, the easiest way to handle these is to right click on your region (after volume mesh is complete) and select 'remove invalid cells'. This will bring up a dialog and you can configure it to remove all cells with volume less than zero. These will now show up as separate regions in your model, but can be ignored. The model should run fine after that.