Computational Heat Flux Predictions for the AFOSR BOLT-II Flight Test

Abstract

The BOundary Layer Turbulence (BOLT-II) flight experiment proposed by the Air Force Office of Scientific Research (AFOSR) is a joint collaboration between academia, industry, and government partners to advance the understanding of hypersonic boundary layer turbulence on a concave surface with highly swept leading edges. To perform such a test at hypersonic speeds a large amount of aerodynamic analysis must be done before flight to assess the mechanical and thermal loads expected on the vehicle and analyze what effects they could have on the vehicle being flown. One of the largest challenges when performing these analyses is quantifying thermal loading on the transition between BOLT-II and the rocket system being flown on. To analyze these thermal loads a set of computational fluid dynamics (CFD) simulations were performed in the US3D code using structured grids generated in the Pointwise meshing software. A convergence study was performed on a quarter symmetry mesh to iteratively design a mesh with the ability to simultaneously capture the laminar sub layer and generate grid independent solutions of wall heat flux. The research in this thesis focuses on using these CFD simulations to quantify heat flux on the fairing and payload bay at critical points identified on the BOLT-II flight test trajectory in support of thermal protection (TPS) calculations at the Calspan-University of Buffalo Research Center (CUBRC) and Johns Hopkins University Applied Physics Laboratory (JHAPL). To determine the dependence of heat flux results on the selected turbulence models additional CFD simulations were run using an alternate turbulence model to quantify the difference in heat flux calculated using the two turbulence models. To analyze the validity of heat flux data CFD results were compared to heat flux calculated from wind tunnel tests on a 25 percent scale model of BOLT-II, the fairing, and sections of the payload bay using IR thermography and a 1D heat flux analysis code. This comparison showed agreement between major heat flux features observed in CFD and wind tunnel tests providing evidence that qualitatively supports CFD results. From these results recommendations are made concerning further tests that could be performed to improve information gained from this study.