Effects of Attitude on HIFiRE-5b Boundary-Layer Transition

HIFiRE-5 is a hypersonic flight-test experiment designed to investigate the aerothermodynamics of a three-dimensional geometry. The vehicle is an elliptic cone with a 2:1 aspect ratio and 2.5 mm nose radius. The HIFiRE-5b achieved a Mach number of 7.7 to 7.9 and freestream unit Reynolds number of 5.106/m to 50.106/m during descent. Heat flux was calculated from thermocouple pairs, and boundary-layer transition locations were identified from these heating rates. A multilobed transition front was observed; it is suspected that a different mechanism is responsible for each of these lobes. The first round of flight-test data analysis did not control for attitude variation, resulting in oscillating heat-flux rates. The current work subsamples the data based on angle of attack and yaw, enabling a more precise investigation of other relevant variables. Regions of the flowfield especially sensitive to attitude variation can be better analyzed. The heating rate at the leading edge exhibits the expected dependence on yaw angle and insensitivity to angle of attack. Data from the crossflow-dominated portion of the flowfield show the region's sensitivity to angle of attack and dependence on yaw. Transition near the centerline exhibited a small dependence on angle of attack, but a large effect from yaw.