Hypersonic non-equilibrium Computational Fluid Dynamics (CFD) analysis and effect of underbelly shape on a conceptual lifting body spaceplane

Abstract

A methodology is developed to analyse the effect of underbelly shape on the force coefficients and adiabatic wall temperature acting on a lifting body spaceplane at 30° angle of attack and three Mach numbers (𝑀𝑎=4, 10, 16) in air in the commercial Computational Fluid Dynamics (CFD) solver, Ansys Fluent. A general overview of hypersonic theory and phenomena is also presented. The effect of hypersonic flow on gas dynamics is considered using a two-temperature non-equilibrium energy model and species transport simulation of reacting gases in Ansys Fluent. No third-party research of note is found validating the two-temperature Ansys Fluent non-equilibrium energy model due to only being recently implemented in 2021. Therefore, a focus of the investigation is validating the model against empirical results. Validation of the numerical and physical models is performed by comparison against empirical wind tunnel investigations and flight data for simple shapes. Domain and mesh sensitivity studies are performed. CFD simulations of a blunt cone at Mach 6.77 matched a wind tunnel validation case by within 15-20% for lift and drag coefficients, and matched lift-to-drag ratio by 1-3%. CFD of ELECTRE test vehicle validation case matched flight data stagnation point heat flux to within 1%. An attempt was made to determine the adiabatic wall temperature of a space vehicle re-entering from low Earth orbit, but poor agreement with theory was reached – suggestions are made to explain this, and recommendations for future work are discussed.