Onset of condensation in vortical flow over sharp-edged delta wing

Onset of condensation in a streamwise vortex generating from the leading edge of a single-delta wing in atmospheric wind tunnel and flight conditions is numerically investigated. The fundamental equations are based on the compressible Navier-Stokes equations and additional conservation laws of water vapor, water liquid and the number density of nucleus. Homogeneous nucleation and nonequilibrium condensation are modeled by the classical condensation theory. Also heterogeneous nucleation is approximately taken by assuming a finite number of nucleus with a constant radius into consideration. A maximum fourth-order space-accurate and second-order time-accurate high-resolution finitedifference scheme is implemented for solving these equations. Three-dimensional subsonic flows over the 76° sharp-edged single-delta wing without thickness are calculated as the free-stream Mach number and the atmospheric conditions are varied. The calculated results present that the onset of condensation in the streamwise vortex is very sensitive to these conditions. The onset point of condensation is very influenced by the inlet Mach number in the atmospheric wind tunnel conditions. The present results of the onset assuming heterogeneous nucleation, however, present that the influence of the inlet Mach number is relatively trivial compared with the flow assuming the homogeneous nucleation in the atmospheric wind-tunnel conditions. Consequently, the onset of condensation may depend deeply on the assumption of nucleation process.