Laminar Boundary-Layer Instabilities on Hypersonic Cones: Computations for Benchmark Experiments

Abstract : Although significant advances have been made in hypersonic boundary-layer transition prediction in the last several decades, most design work still relies on unreliable empirical correlations or wind-tunnel tests. Codes using the semi-empirical eN method will need to be well verified and validated before being used for expensive flight vehicles. The code package STABL and its PSE-Chem stability solver are used to compute first and second-mode instabilities for both sharp and blunt cones at wind-tunnel conditions using a Xavier-Stokes mean-flow solution. Computations are performed for Stetson's 3.81 mm nose-radius cone, a sharp cone at Mach 3.5, a large-bluntness cone at Mach 8, and sharp and blunt cones corresponding to the experiments of Rufer. Comparisons to previous computations by other researchers show differences on the order of 10% in local amplification rates and frequencies, but better agreement is obtained for the transition location. Many issues are examined for verification and validation, including the laminar transport properties, the freestream boundary conditions, and the effect of freestream thermal nonequilibrium. This work helps to verify and validate STABL, extend its applicability to low-temperature flows, and develop the methodologies for using STABL.