Steady and Unsteady Condensation Phenomena in a Prandtl-Meyer Flow.

In this paper a two-dimensional supersonic flow field with continuous energy supply is investigated. The experiments are carried out in a transonic wind-tunnel for intermittent operation. The heat supply is accomplished by condensation of water vapor, which is added to the flow upstream of the test section. At the onset of condensation the flow properties change. This change depends on the relative humidity of the air and the amount of the added heat. By interferometric measurement of the flow field the Mach number at the onset of condensation can be determined. With the aid of the experimental investigations the dependency of the condensation onset Mach number on the relative humidity of the flow can be estimated. Thus the beginning of the unsteady flow conditions can be calculated for a given nozzle geometry.