Evaporation of a rarefied gas from a cylindrical condensed phase into a vacuum

Abstract

Steady evaporating flows from a cylindrical condensed phase into a vacuum are studied on the basis of kinetic theory. The behavior of the gas (the velocity distribution function as well as the density, velocity, and temperature) is analyzed numerically in detail for the whole range of the Knudsen number defined by the condition of the condensed phase. The discontinuity of the velocity distribution function in the gas, a typical behavior of the gas around a convex body, is analyzed accurately. The flow is highly in nonequilibrium over the whole field except for very small Knudsen numbers. The behavior of the far field from the cylinder, proper to each Knudsen number, differs markedly from that of corresponding flow [Phys. Fluids A 5, 1491 (1993)] from a spherical condensed phase, universally of free molecular type. The height of the velocity distribution function and the temperature of the gas vanish at infinity, without freezing at finite values, except in the free molecular flow.