Application of Broadband Receptivity Data to the Amplitude Method for Transition Prediction

Abstract

Conventional hypersonic transition prediction relies upon the highly empirical method, which is predicated on theoretical approximations of relative disturbance growth. This does not account for the receptivity mechanism and the high degree of variability present in experimental wind-tunnel conditions, which itself leads to high degrees of variability in transition factors. The amplitude method, which better approximates the broadband nature of boundary-layer disturbances, was previously proposed to account for the effects of receptivity. In this study, high-fidelity simulated second-mode receptivity data for two blunt cones at Mach 10 to broadband disturbances are applied to an iterative approximation of the amplitude method tuned for second-mode dominated flows. The studied geometries consist of 9.525- and 5.080-mm-nose-radius 7 deg half-angle straight cones based on experimental cases from Arnold Engineering Development Center’s wind tunnel 9. Amplitude method predictions show improvement over the accuracy of estimates using standard threshold factors. In particular, the less blunt 5.080 mm cone demonstrates the best agreement due to its stronger second-mode response. The results of this work provide a preliminary framework for applying high-fidelity receptivity simulations to the amplitude method for transition prediction in hypersonic flows.