Hypervelocity aerothermodynamics of blunt bodies including real gas effects

摘要

Hypervelocity aerothermodynamics of blunt bodies such as a circular cylinder and a 45◦ half-angle blunted cone have been investigated experimentally, analytically, and numerically. Particular emphasis was placed on the base region. A broadrange of flow conditions varying from suborbital to superorbital speeds that cover from low to high enthalpies were generated. The experiments consisted of surface pressure, heat flux, and flow visualisation. Low to moderate enthalpy suborbital flow conditions were generated in the T-ADFA shock tunnel over a circular cylinder. The test gas was air. High enthalpy superorbital flow conditions were generated in the X2 expansion tube over a blunted cone. Two test gases were examined - One air and the other a mixture 96%CO2-4%N2 (simulating the Martian atmosphere). The cylinder experimental data showed good agreement with the present laminar near wake theory based on perfect gas, indicating that in the low to moderate enthalpy flows, the chemistry effects in the base region are not significant. Unlike the surface pressure, the surface heat flux depended strongly on wall to total temperature ratio. It increased with increase in the ratio. The surface pressure, however, depended on the Reynolds number although this dependency was found to be weak at hypersonic speeds. The flow separation angles showed a linear variation with the inverse of the square root of Reynolds number similar to the low speed laminar flow separation behind a circular cylinder. The reattachment distance showed a dependency on the freestream Reynolds number and the wall temperature. As regards the forebody flow of the blunted cone, the measured surface pressure and heat flux showed good agreement with the Navier-Stokes code based numerical results that included the effects of chemistry. In the base region, it was found that the chemistry effects are stronger on the base and in the near wake for the case of Martian atmosphere compared with those in the near wake for air. The theoretical results showed good agreement as regards the base pressure but the heat flux predictions were somewhat under predicted but still reasonably close to reacting gas numerical calculations.