Experimental study on the boundary layer transition of a high-speed fin-cone configuration

Abstract The high-speed boundary layer transition directly affects the refined design of the flight vehicle’s aerodynamic and thermal properties. However, current research in this field generally focuses on simplified geometries, such as cones or flat plates, resulting in a limited understanding of high-speed boundary layer transition in practical vehicle configurations. This study aims to carry out an in-depth investigation of high-speed boundary layer transitions in a fin-cone configuration with a double-cone design. PCB sensors are used to characterize the evolution of instability waves along the streamwise direction on both the leeward and windward sides of the model. Additionally, focused laser differential interferometry (FLDI) is deployed to measure the instability characteristics along the wall-normal direction of the high-speed boundary layer. Furthermore, an infrared camera is employed to obtain surface temperatures. In addition to the second-mode instabilities observed on the leeward side, streamwise vortex-induced local peaks on the windward side are also observed with PCB sensors. Infrared images reveal that the thermal characteristics are different between the windward and leeward sides due to transition mechanisms. The study reveals that at similar Reynolds numbers, the area fully developed to turbulence on the windward side is considerably larger than that on the leeward side for the cone region, while the fin region displays different trends. These findings provide invaluable insights for the advancement of aerodynamic and thermal design in high-speed aircraft.