Experimental Investigation on Heat Streaks Behind a Swept, Second-Order Continuous Leading Edge in Hypersonic Flow

To further investigate the formation and behavior of streamwise heat streaks in hypersonic flow, a simplified highly-swept model with a second-order continuous leading edge was tested in the Actively Controlled Expansion (ACE) hypersonic tunnel at Texas A&M University. The study aimed to examine the effects of shock curvature and the influence of second-order leading edge continuity on heat streak behavior at Mach 5.7 across a variety of pitch angles and Reynolds numbers. Diagnostic techniques for analysis included high-speed schlieren, infrared thermography, and surface-mounted pressure transducers. The results showed that heat streaks developed along the test article’s surface, with their intensity increasing with both Reynolds number and angle of attack. The streaks were less intense and appeared further downstream compared to those observed on geometries with second-order discontinuous leading edges under identical conditions. In addition, their spanwise location shifted inward with increasing angle of attack. Surface pressure spectra revealed broadband disturbances from 15 to 50 kHz at various positions along the model, with characteristic frequencies remaining constant but intensities scaling with flow conditions. These findings suggest that, while second-order continuity of the leading edge may reduce initial shock curvature concentrations, it does not solely eliminate the generation of vortical structures responsible for localized heating in laminar hypersonic flows. Spanwise pressure gradients and the turning radius of the corner, regardless of the continuity of the leading edge, play a key role in the formation of heat streaks.