Competition between thermophoretic deposition and erosion leading to appearance of steady coating

A theoretical and experimental study of two-phase flow with bimodal ("coarse" and "fine") spherical particle distribution was carried out. Deposition of the particles onto a plate inclined at some angle to the flow direction at infinity is considered. The plate temperature being lower than that of the gas at infinity, the fine particles are thermophoretically deposited onto the plate surface and a coating accumulates on it. As the coarse particles impinge inertially upon the coating, the top layer of the latter is eroded and its thickness decreases. It is shown that the competition of these two processes (thermophoretic deposition and growth vs inertial impingement and erosion) may lead to a steady-state situation, which is of practical interest, for example, in creating a self-regulating layer on turbine blades in the polluted gas streams accompanying coal combustion.