BoLT II ground tests with leading edge preheating

Abstract: The BoLT geometry was developed to obtain flight data on transitional and turbulent boundary layers for a complex, three-dimensional geometry at hypersonic flow speeds. The BoLT II mission was flown successfully in March 2022, reaching Mach 6 flow conditions. That model experienced aerodynamic heating during the flight, resulting in the leading edges of the model reaching temperatures as high as 990 K. No ground testing experiments had been undertaken to investigate if such heating influences the transition process. The goal of the present study was to heat the nose region of the BoLT II geometry in tests in the T4 Stalker Tube at The University of Queensland and to measure the effect of heating on transition using thin-film heat-transfer gauges. Nose temperatures of up to 509 K were achieved in tests in which the Reynolds number based on the length of the model was varied from 1.13e6 to 5.11e6. Results indicate little influence of heating to this level on the transition process on the model. Keywords: Boundary layer transition, model heating, shock tunnel, BoLT II