Hypersonic Conceptual Design Tool Comparison PDF Download

The many iterations needed to explore a design space in the conceptual design process preclude the use of time-consuming RANS CFD for all but a few flight conditions. This research focuses on identifying the level of fidelity needed to adequately predict the aerothermodynamic characteristics of hypersonic vehicles. Three tools with differing levels of fidelity - CBAERO, Cart3D, and Kestrel - were used to analyze the Generic Hypersonic Vehicle (GHV) at the design condition of Mach 5.85 and an off-design condition of Mach 4.5. The results are representative of the different design tools but are not definitive due to the mesh size in Kestrel being limited by the available computational resources. The results obtained show a large difference in the unstart threshold predicted by inviscid and viscous CFD: 21° vs 11.75° degrees for Mach 5.85 and 14.5° vs 6.5° for Mach 4.5. Despite that difference, all three methods showed reasonable agreement for CL, CD, and CM across the entire range. The medium-fidelity method, Cart3D, was also capable of matching Kestrel's mass capture below the unstart threshold. The heat flux from the reference temperature method with Cart3D overestimated the heat flux on the bottom surface and underestimated heat flux on the top surface compared to Kestrel. At low angles of attack it appears to provide a heat flux estimate with a natural factor of safety, but it risks leading to overdesigning at higher angles of attack. The high-fidelity method, Kestrel, only showed significant differences from the lower fidelity methods in the unstart threshold, L/D, mass capture after unstarting, and heat flux at high angle of attack.