Wall region turbulent flow under high mass fluxes over a flat plate

Abstract

In mass transfer operations, the surface, past which the fluid moves has the additional property of acting as the source or sink of material for the flowing stream. The diffusing molecules carry momentum with them, which effects the original velocity distribution, which in turn effects the mass transfer process itself. The problem of mass-transpired boundary layers in turbulent flow has been analyzed with particular emphasis on the region in the immediate vicinity of the wall. The combined effect of the viscous and turbulent stresses has been taken into account. Theoretical results have been expressed in terms of the dimensionless velocity, U +, and eddy viscosity, ϵ/ν as a continuous function of the dimensionless distance parameter y +. It is observed that the effect of the turbulent stresses is substantial, particularly at high transpiration rates. It is also shown that substantial differences, mainly in the case of injection, exist between the momentum profiles of an external and internal flow system. It has been also concluded that the eddy diffusivity close to the wall varies with the cubic power of the distance measured from the wall under both low and high mass flux conditions.