Rob
Ansys Employee

 

Number of parcels trapped v injected? Did you use scale by area on the injection? The reason for asking is scale adjusts the parcel mass per facet so you may find the parcels have a different weight so you need to monitor mass. If you don’t scale, you may also be adding more streams around the perimeter (inflation mesh) so skew the results. It’s not a simple application to model: the set up is simple, the physics somewhat less so. 

There's also the issue of small particles penetrating the viscous sub layer, and that wall contact is only checked once the particle is in the near wall cell. So, well resolved (y+ = 1ish) meshes may not be what you want.