Particle tracking issue with CFX
 

I am simulating particle transport in CFX. I have geometry of 10 channels of size 40 microns. I was releasing particles in the range of 2-10 microns dia. Just to test the authenticity of the software I bumped the dia all the way up to 45 microns and was expecting the channels to block the particles. But that didn't happen. I even tried refining the mesh grid but in vain. Help???
(It's the same issue with COMSOL)

The particle transport models are not valid for cases like that. CFX does not compare the particle diameters to the geometric or element sizes; it assumes you are using the software properly, i.e. that the particle diameters are small compared to the element sizes.