I have an unbaffled stirred tank reactor with a shaft and paddle rotating at 200 rpm. I have used MRF and realizable k-e to get a steady state solution. I have then used the discrete phase model to track a single particle dropped onto the free surface of the liquid. I have set the number of steps to 3x10^6 and the step length factor to 20. There are no inlets or outlets. I get a calculated residence time of approx 45s. However, when I view the particle track, I see the particle descending through the fluid in a circular fashion around the shaft until it hits the face of the paddle. When it hits the impeller it just stops as if it is trapped. This is confusing because in the Define-Boundary Conditions box, all walls are set to reflect and so is the impeller and the shaft. The impeller is stationary and the fluid is rotating (as I said, I have modelled using MRF).

Does anyone have any idea why this is happening? It's driving me completely mad!!! Any and all ideas gratefully received.

are u using stochastic tracking?

regards

zachi!

i use stochastic tracking.

check the wall reflection coefficients in the wall boundary conditions panel. if they are zero it would cause particles to stop.

[Arjun kumar P]

Hi, I am also facing similar situation. Can you tell me how did you circumvent this challenge. Particles sticking to the wall!!