Transition in the Hypersonic Boundary Layer

The transition in the hypersonic boundary layer represents a pivotal area of interest within the fluid mechanics community. This talk provides a review of the recent advancements in hypersonic boundary-layer transition studies, encompassing research facilities and experimental methodologies. It introduces the hypersonic quiet wind tunnel as an essential tool for acquiring near-space real flight data. Techniques for near-wall measurement, including temperature-sensitive paint, near-wall particle image velocimetry, infrared thermography, and Rayleigh-scattering visualization, are explored. The talk addresses critical issues in hypersonic boundary layer transitions, focusing on the instability and nonlinear interaction among various instability modes. It proposes the phase-locked mechanism of these instability modes and introduces a novel principle of aerodynamic heating in hypersonic flows. Additionally, it thoroughly discusses the structural formation of boundary layers over flat plates, sharp cones, flared cones, and delta wings.