Discrete Phase Model - Particle Tracking
 

I have modelled an unbaffled stirred tank reactor using the MRF technique and the realizable k-e turbulence model. I am then using the discrete phase model (DPM) to add an injection of a single inert particle. The particle is effectively trapped within the vessel and so its trajectory will always be incomplete. I have tried many different combinations of number of steps and length scales in the DPM panel, however, the maximum residence time I have acheived is 21 seconds using 30,000 steps and a step length factor of 1 (after 21 seconds the results alternate between two values and so are meaningless). Ideally I would like to model the particle trajectory for several minutes (up to 20 if possible). Please advise if this is possible and, if so, how it might be acheived.