OVERVIEW

Suspended particles may not be able to follow the motion of an accelerating gas because of their inertia. This effect is most important for particles larger than 1 ?m. It may lead to particle deposition on surfaces, a process known as intertial deposition. Inertial deposition is often the controlling mechanism for the removal of larger particles in gas-cleaning devices, such as filters, scrubbers, and cyclone separators. In filters, inertial deposition occurs when the gas flows around the individual fibers or grains composing the filter. The particles that cannot follow the air stream impact on the collecting element. In scrubbers, the collecting elements are water droplets, whereas in cyclone separators, it is the rotating gas stream that deposits the particles on the wall. In each case, it is the acceleration of the gas that leads to deposition. Inertial effects also play a role in atmospheric processes such as rain scavenging and deposition on vegetation and man-made structures.

Unlike diffusion, which is a stochastic process, particle motion in the inertial range is deterministic, except for the very important case of turbulent transport. The calculation of inertial deposition rates is usually based either on a force balance on a particle or on a direct analysis of the equations of fluid motion in the case of colliding spheres. Few simple, exact solutions of the fundamental equations are available, and it is usually necessary to resort to dimensional analysis and/or numerical computations. For a detailed review of earlier experimental and theoretical studies...