Effect of Micro-Blowing on Turbulence Characteristics in Hypersonic Boundary Layers

Micro-blowing has emerged as a promising flow control technique for turbulent boundary layers, offering potential for reducing both skin friction and aerodynamic heating. While its effectiveness has been demonstrated in incompressible and supersonic regimes, its application and underlying mechanisms in hypersonic flows remain insufficiently understood. In this study, Mach 6 turbulent boundary layers were experimentally investigated under various micro-blowing intensities using wind tunnel tests and Particle Image Velocimetry (PIV). Comparative analysis of vertical profiles of total pressure, Mach number, and mean streamwise velocity revealed a clear expansion of the low-momentum region with increasing blowing intensity. Despite an increase in turbulent kinetic energy, the Reynolds shear stress showed a notable reduction in magnitude and an upward shift of the constant-stress layer to approximately [Formula: see text], implying a weakening of near-wall momentum transfer and a corresponding reduction in friction velocity. The spatial evolution of the boundary layer thickness and streamwise velocity deficit demonstrated that the influence of micro-blowing progressively weakens along the streamwise direction. Furthermore, two-point correlation and inclination angle analyses indicated that micro-blowing enlarges the coherent turbulent structures and reduces their inclination relative to the wall, reflecting substantial alterations to near-wall turbulence dynamics. These findings provide new experimental insights into the structural modulation induced by micro-blowing in hypersonic boundary layers and reinforce its potential as a viable strategy for reducing drag and thermal loads in high-speed aerodynamic applications.