TRANSONIC AERODYNAMICS INCLUDING STRONG EFFECTS FROM HEAT ADDITION

Gasdynamic phenomena in transonic flows caused by the phase transition of the fluid components of vapor/carrier gas mixtures and pure vapors have been investigated in theory and experiment. The dominating param eters, the cooling rate of the expansion and the reservoir conditions (vapor pressure) are varied to investigate the coupled process of the nonequilibrium phase transition after homogeneous nucleation and the e quilibrium condensation in flows near a Mach number of unity. The nume rical code is applied to compute transonic flows of water vapor/carrie r gas mixtures in indraft wind tunnels and in atmospheric flight, flow s of nitrogen vapor in cryogenic wind tunnels or shock tubes and the e quilibrium condensation process in flows over airplane wing sections. The computation of the inviscid flow field is based on an explicit fin ite volume method that solves the time-dependent 2-D Euler equations l inked with the classical nucleation theory and microscopic or macrosco pic droplet growth laws. Turbulent boundary layer calculations demonst rate viscous effects and the development of the nonequilibrium phase t ransition in shear layers. Emphasis is given to supercritical rates of the heat release and shocks inside the nucleation zone and acrodynami cal shocks with evaporation of the condensate. The main contribution i s achieved from the phase transition in the inviscid flow with rates o f heat addition q/c(p) T01 typically < 10%. Nevertheless, transonic fl ow fields become seriously affected and the pressure drag and lift of airfoils change up to 60%. The sign of these variations changes sensit ively with the free-stream Mach number and the angle of attack. Atmosp heric flight condensation processes develop near equilibrium and cause a significant increase in the pressure drag. Computations on the basi s of given heat source distributions show that homogeneous nucleation initiates heat release to the flow just in the most sensitive region o ver the airfoils.