Detached Eddy simulation of hypersonic base flows during atmospheric entry

The objective of this paper is to present preliminary results of our efforts to simulate the turbulent flowfield of the Reentry-F flight experiment. To do this, we employ the Detached Eddy Simulation methodology coupled with an implicit, shock-capturing, Navier-Stokes solver and five-species chemical kinetics model for air. The simulations were performed for two altitudes, 80 and 70 kft, corresponding to freestream unit Reynolds numbers of 18.5 × 10⁶ and 30.1 × 10⁶ per meter, respectively. Forebody calculations incorporated boundary layer tripping and are shown to give good results at 80 kft, however the laminar and turbulent heating is overpredicted at the lower altitude. This is believed to be caused by assuming axisymmetry while the actual vehicle was at approximately 0.5° angle of attack. Three-dimensional base flow calculations were performed and showed rather poor agreement with experimental data. At 80 kft, the turbulence model failed to capture the base flow instability, resulting in a slightly unsteady vortical flow attached to the afterbody. Comparisons with measurements showed heating rates and pressure to be significantly overpredicted due to the presence of a disk shock. At 70 kft, the model responded more favorably, although our preliminary comparisons with data showed heating rates to be underpredicted. A number of factors may contribute to these results. Among them are the lack of an angle of attack in the simulations, modeling assumptions in the base geometry, the potential need of an Unsteady inflow to excite the flow instability, and the validity of the RANS model near the base. Addressing these concerns is the subject of ongoing work.