I would agree with nan ussually indicating there is an issue. The particles should be rising. They are entering through several surfaces located just below an impeller blade (the upturned shower head region). I decreased my time step for each of my simuation sets. For the set with a lower inlet velocity, the simulation is advancing (for how long, I do not know). For the simulation set with an inlet velocity an order of magnitude greater the model has issues at the DPM update.