Applications of Underexpanded Jets in Hypersonic Aerothermodynamics Research

A method of underexpanded hypersonic viscous jets has been developed to acquire experimental aerodynamic data for simple-shape bodies (plates, wedges, disks, and others) in the transitional regime between free-molecular and continuum flow regimes. The kinetic, viscous, and nonequilibrium processes in the jets of He, Ar, N2, and CO2 under various experimental conditions have been analyzed by asymptotic methods and numerical techniques. Fundamental laws for the aerodynamic characteristics and similarity parameters are revealed. In the case of hypersonic stabilization, the Reynolds number and temperature factor are the main similarity parameters. This research has discovered those conditions, which allow the significant influence of other parameters (specific heat ratio, viscosity parameter, Mach number). The acquired data could be used effectively for research and prediction of aerodynamic characteristics of vehicles during hypersonic flights under the rarefied atmospheric conditions of Earth, Mars, Venus, and other planets.