SIMULATION TECHNIQUES IN HYPERSONIC AEROTHERMODYNAMICS

摘要

Hypersonic viscous flows near simple-shapebodies (wedge, cone, disk, plate, sphere, androtating cylinder) have been studied under theconditions of wind-tunnel experiments andhypersonic flights. The Direct SimulationMonte-Carlo technique has been used to studythe influence of similarity parameters onaerodynamic coefficients in hypersonic streamsof air, nitrogen, helium, and argon. It has beenfound that, for conditions approaching thehypersonic stabilization limit, the Reynoldsnumber and temperature factor are primarysimilarity parameters. The influence of otherparameters (specific heat ratio, Mach number,and viscosity parameter) becomes significant atlow Reynolds numbers (less than 10) and smallvalues of the hypersonic similarity parameter(less than 1). The numerical results are in agood agreement with experimental data, whichwere obtained in a vacuum chamber atReynolds numbers from 0.1 to 200. The effectof nonequilibrium processes on simulation ofthese flows over blunt bodies has been studiedby solving the full Navier-Stokes equations andthe viscous-shock-layer equations. Thenonequilibrium, equilibrium and 'frozen' flowregimes have been examined for variousphysical and chemical processes in air andnitrogen, including excitation of rotationaldegrees of molecular freedom, chemicalreactions and ionization. It has been found thatthe binary similitude law is satisfied for bluntbodies in the transition flow regime.