Fundamental modes of particle impaction on a solid object

In this work three fundamentally different modes of particle impaction on a cylinder
in a cross flow is presented. Large particles impact on the cylinder in the so-called classical mode
where the impaction efficiency is controlled by the particle inertia and the large scale fluid motions.
For intermediately sized particles the thickness of the boundary layer around the cylinder is determining
if a particle will impact on the cylinder surface or not. In this boundary stopping mode, the
Reynolds number is important for the impaction efficiency. Finally, the smallest particles follow
the flow perfectly around the cylinder, but due to their finite radius, some of them will nevertheless
be intercepted. This is the boundary interception mode, and it is likely to be susceptible to
secondary effects such as electrostatic forces, skin effects, surface roughness etc. Additionally, the
effect of turbulence in the fluid flow is shown. It is found that for the relatively small Reynolds
numbers investigated the effect of the turbulence is seen only in the boundary stopping mode.