COMPARATIVE SIMILARITY ANALYSIS OF HYPERSONIC RAREFIED-GAS FLOWS NEARSIMPLE-SHAPE BODIES

Hypersonic viscous hows near simple-shape bodies (wedge, cone, disk, a nd plate) have been studied numerically under the conditions of wind-t unnel experiments with underexpanded jets. The direct simulation Monte Carlo technique has been used to study the influence of similarity pa rameters on the flow structure near the bodies and on the aerodynamic coefficients in hypersonic streams of air, nitrogen, helium, and argon . It has been found that, for conditions approaching the hypersonic st abilization limit, the Reynolds number and temperature factor are prim ary similarity parameters. The influence of other parameters (specific heat ratio, viscosity-approximation parameter, and the Mach number) b ecomes significant at low Reynolds numbers (less than 10) and small va lues of the hypersonic similarity parameter (less than 1). The numeric al results are in good agreement with experimental data, which were ob tained in a vacuum chamber at low and moderate Reynolds numbers from 0 .1 to 200. In the studies of the pitching moment and lift coefficients , a three-dimensional numerical approach should be used to simulate no nuniform flow near a plate, cone, and wedge under the experimental con ditions with freejets.