Examination of Nonequilibirum Effects at High Mach Number and Stagnation Enthalpy for Double Cone Model - Part III

The sharp leading edge 25-55 double cone model has been examined on the effects of nonequilibrium thermochemistry in a high Mach number and stagnation enthalpy environment via a computational study. This computational study uses the Shot 292 experiment of Kennedy et al. in the University of Queensland's X-3 expansion tunnel as an experimental basis for freestream and model surface conditions. A previous computational study was conducted by the authors for the Shot 294 experiment of Kennedy et al., which showed that nonequilibrium effects, through the usage of a two-temperature model and Park I thermochemistry, did not accurately predict surface pressure or heat flux while a thermally perfect (nonlinear gas properties) model was sufficient for both. With these previous results, a thermally perfect model is used to evaluate the surface pressure and heat flux. A mesh convergence study was conducted to verify that solution convergence was accurate and within experimental uncertainties. Along the forward cone, surface pressure is in good agreement with the experimental results while heat flux is underpredicted. The location of boundary layer separation is in good agreement. Size and surface values of the separation region are in good agreement with experiment. The maximum magnitude of surface pressure exceeds that experimentally measured which is the likely case. This is emphasized by the computed maximum location being slightly forward of the maximum measurement location where the pressure at the experimental location is in good agreement. Evaluation of the agreement of heat flux is difficult due to asymmetries in the experimental data. The computed maximum heat flux is estimated to be greater than all of the experimental maximums, however, the predicted and experimental locations are in good agreement. One important measurement location is that immediately preceding to the maximum heat flux, which the computation underpredicts. This location corresponds to a second separation region induced by the shock-wave boundary layer interaction. The region along the aft cone after the shock-wave boundary layer interaction location is in fair agreement with experimental surface conditions illustrating an oscillating behavior in both surface pressure and heat flux, however, does underpredict the experimental surface heat flux. From the computed flow field there is formation of a Mach stem with the shock wave-boundary layer interaction shock between the wall and subsonic region aft of the bow shock until two λ-shocks form along the slip line between the supersonic jet generated by an Edney type IV shock-shock interaction and post-bow shock supersonic flow. The downstream λ-shock is sufficiently strong to produce a second subsonic region and interacts with the bow shock to transition it to a conical shock.