Nonlinear Theory III — Finite Speed of Evaporation and Condensation

Abstract

In the preceding chapter, we have discussed a flow with a finite Mach number around a simple boundary, across which there is no mass flux. In the present chapter we consider a flow of a gas around its condensed phase where evaporation or condensation with speed of a finite Mach number is taking place. Owing to the convection effect of condensing or evaporating flow of the order of the Mach number, the viscous boundary layer, which appears in a flow with a finite Mach number around a simple boundary (Chapter 6), shrinks to merge into the Knudsen layer over a condensing boundary, or the layer spreads into the whole flow field (or the Euler region) over an evaporating boundary and the viscous effect is reduced to a secondary one there. The Euler region is connected directly to the Knudsen layer. Instead, the Knudsen layer is governed by a nonlinear equation in contrast to that in the foregoing chapters.