Diffusion Deposition on a Fiber in Nontransverse Flow

The effect of a nontransverse flow on the diffusional deposition of particles in an aerosol on a cylindrical fiber is investigated. The aerosol is transported by a slow laminar flow whose mean direction is at an arbitrary angle ? to the axis of the cylinder. The particle concentration and the subsequent deposition rate on a cylinder for such a flow are found by using the first two terms of the asymptotic solution in terms of the diffusion boundary layer thickness. This is inversely proportional to the cube root of the Peclet number, a parameter which is large for many problems of practical importance. For a given flow angle ? an expression for the diffusion efficiency η(?) is obtained. Under the assumption that the angular distribution of the fibers is uniform, a relation for the average value (η) for the diffusion efficiency is also derived. These formulas are generalizations of the results of Natanson and Stechkina for the diffusion efficiency in the case of purely transverse flow and with those of Banks and Kurowski for the mean flow at a small angle to the fiber