Don't use CFD Post, do the post processing in Fluent. Post is good for large transient data sets but otherwise I'd leave it.
In the DPM model we assume the particle volume fraction is small (overall) but also that particles are small compared to the cell size. I don't know how big the domain is, but 18mm diameter particles could be big relative to the mesh.
The particle does not have a velocity profile. Each track will have a velocity with length (or duration). Or each particle will have a velocity at each time step. Not sure what you're after.
Finally, please don't log multiple threads on related questions. It makes helping difficult, and may mean we duplicate work: that's annoying.
You are navigating away from the AIS Discovery experience