Evaporation from a cylindrical surface into vacuum

Abstract

When evaporation takes place in a surrounding vacuum, the expanding flow from a cylindrical surface is expected to start subsonic and to become supersonic in a short distance. A detailed treatment of this transition is given based on moment equations derived from the BGK model equation using an ellipsoidal approximant to the distribution function. Asymptotic solutions are developed for large source Reynolds numbers and compared with previous treatments. For moderate source Reynolds numbers a numerical procedure is used. In the latter case the treatment predicts that the flow never approaches a state of translational equilibrium.