Seed particle and trap it in a channel by CFX
 

I want to introduce the particle liquid into the micro-channel, which built by some trap(70um), the particle diameter from 20um~80um, when the flow through the bigger particle(70~80um) would trapped in the trap, and the smaller through traps, the trapped particle could make effect to the flow(two-way?)

After that I need a animation that trap the bigger particle and the smaller through the channel.

How do I set the condition in the CFX??

Thanks