Experimental investigation of the expansion of moist air around a sharp corner

The results of an experimental study of two-dimensional supersonic expansions of moist air around a sharp corner are reported. Condensation of water vapor by homogeneous nucleation occurs within the expansion fan. Measurements of the location of the onset of condensation show that the leading edge of the condensation zone is concave with respect to the oncoming flow. Density measurements, obtained from the analysis of flow-interfer ograms, indicate that the flowfield within the condensation zone is a function of both expansion angle and radial distance from the corner. An empirical relation between experimentally determined adiabatic supercooling and expansion cooling rate is obtained. Nomenclature C = constant, Eq. (5) h* = nozzle throat height K = Gladstone-Dale constant L = optical path length M = Mach number n = exponent, Eq. (5) p = pressure R = universal gas constant r = radial distance measured from the corner A$i2 = nondimensional fringe shift T = temperature ATad = adiabatic supercooling 7 = ratio of specific heats X = wavelength JLI = molecular weight p = density 3> = relative humidity <£ = expansion angle measured from the vertical at the corner a) = specific humidity Subscripts a = air c = saturated conditions, condensed phase k = onset of condensation v — water vapor 0 = stagnation conditions 1 = reference conditions 2 = measured properties oo = plane surface