Thanks Rob, I thought it a good idea to shoot for a little under 1 to begin, due to the chance of cells being a bit smaller than my assigned cell, due to the irrgular nature of my grid. When I look at the mesh the smallest grid volume would give me a delta x of about 0.0001 m if I were to assume that delta x =delta y = delta z.
These simulations take a bit of time, due to the small time step, but each continue to run.
Relating to the idea of decreasing the number of cores, do DPM simulations have more success when they are solved in serial? I noticed that in some tutorials they choose to simply use 1 core or process in the model setup.