Hi All - I have been struggling with the transverse velocity profile of the cyclone. I thought that the max velocity was at the cone surface. Which it isn't. The max velocity is at the interface of the inner and outside vortex. Now things make sense. The centrifugal forces push the particle outward. This means the particles are moving into a slower area and as its drag decreases it drops out of the airstream. The particle is either being sweep along in the flow and moving outward in the outer vortex (until it drops out or hits the wall) or if its in the inner vortex its gets accelerated into the outer vortex and the cycle goes on. As the particle moves down the cone the velocity drops further due to the smaller radius. Again at some height level the particle mass overcomes the drag force and it drops out. Can let my brain have a rest now.... Peter