Evaporation from the Surface of a Body in an Airstream (With Particular Reference to the Chemical Method of Indicating Boundary-layer Transition)

Abstract

The problem of predicting the rate of transport of a gas from or into the surface of a two-dimensional body in an airstream is discussed. The principal object of the investigation is to provide a means of estimating the time required to. obtain an experimental record of boundary-layer transition when a chemical technique is used. The methods evolved should, however, find an application to other forced diffusion phenomena. The general approach is based on the analogy between mass transfer, heat transfer and skin friction, and the analysis is applied to both a laminar and a turbulent boundary-layer on the surface of the body; it also includes the problem of diffusion commencing in an established boundary-layer. For this problem, an approximate, alternative solution to that Of O. G. Sutton, for a turbulent boundary layer, is given. Particular attention is paid to a description of the boundary condition at the surface of the body, and it is concluded that, for evaporation, the usual assumption that the air is saturated with the diffusing substance is, in general, satisfactory.