cyclones and particle separation
 

I have a question regarding the settings for coefficients of restitution for particles in cyclone separators. In fluent, you are able to set the normal and tangential "rebound" coefficients. I am currently using normal = 0.3 and tangent = 0.7 as reasonable guesses, but I know these are just educated guesses.

I am encountering several problems with this, including the fact that certain particles continuously contact the outer wall of the cyclone and therefore lose all energy and get stuck (since zero velocity at wall, they never get re-entrained)

Does anyone have any reasonable values from practice, or possibly a guide that they have found useful? I would really appreciate any advice!