Computational Prediction of Aerothermodynamic Characteristics of a Reentry Vehicle at High Angles of Attack

Abstract

The Air Vehicles Directorate of the Air Force Research Laboratory (AFRL/RB) has been investigating reusable launch vehicle (RLV) re-entry trajectory approaches in order to mitigate vehicle heating and improve operability. One approach that has been considered is to fly the re-entry trajectory at extremely high angles of attack (35°-75°), which has been shown to have the potential to reduce peak stagnation and integrated airframe heating. Although wind tunnel tests have been performed to characterize aerodynamic and aerothermal properties at these high angles of attack in hypersonic flows, such testing is very expensive and it is therefore highly desirable to be able perform computational predictions with a high level of accuracy. A study of existing high fidelity computational fluid dynamics codes was undertaken to assess their ability to accurately predict aerodynamic force and moment and aeroheating characteristics of RLVs at high angles of attack in hypersonic flows. Several different organizations using a number of different, but primarily unstructured, codes participated in the study. An initial set of blind simulations was performed by all participants, with computational predictions compared to experimental data once all simulations had been completed. Following the blind simulations and comparison with experimental data, a second set of simulations was performed to improve the results and identify guidelines and lessons learned. For all participants, computational predictions and experimental values for force and moment data showed excellent agreement at all angles of attack. Aeroheating predictions and experimental values showed good agreement, with simulation accuracy highly dependent on grid parameters and operator experience. Nevertheless, the study showed that at these high angles of attack, hypersonic flows can be modeled computationally with very good accuracy for the particular class of vehicle under consideration.