Analysis of External and Internal Aero-propulsive Phenomena in Hypersonic Vehicles

Several parallel efforts were initiated in the first year of the Challenge Project C4D with the goal of computing and understanding the main aero-propulsive phenomena that dominate hypersonic flight. For external transition, stability analyses were performed for the HIFiRE Flight 1. A 7 degree sphere-cone fore body was employed to determine likely transition characteristics and location at different times in the flight path. The implications of a shroud encapsulating the vehicle on placement of the pitot tube were also investigated. Since ground-tests are a major component of the HIFiRE campaign, the effectiveness of large-eddy simulations (LES) in predicting isolator dynamics was evaluated by comparison with experimental data. Finally, high-fidelity, three-dimensional simulations were employed to examine inlet-combustor coupling effects in a scramjet flow path. This is particularly relevant for configurations where the isolator segment is relatively short. Reynolds-averaged Navier-Stokes (RANS) with a k-w turbulence model, as well as LES, were performed with a finite-rate hydrocarbon-air mixture on the integrated inlet and combustor flow path, and compared to sequentially performed situations. The upstream influence of the combustor is considerably larger when the solution is obtained in an integrated fashion and sequential simulations may be overly optimistic in predicting un-start. Parametric studies indicate that reducing the fuel injection and equivalence ratio increases mixing efficiency in certain ranges, while reducing the tendency towards un-start.