Drag and heat reduction in a hypersonic turbulent boundary layer via wall blowing

Hypersonic vehicles are subjected to severe aerodynamic drag and thermal loads during practical flight. To address the issues of high skin-friction drag and intense aerodynamic heating under hypersonic turbulent boundary layer conditions, Large Eddy Simulation (LES) is performed to investigate the drag-and heat-reduction effects of wall micro-blowing through small pores on a Mach number of 6 flat-plate turbulent boundary layer. By comparing smooth-wall and porous-wall configurations, the streamwise distributions of the skin-friction coefficient and wall temperature are analyzed. The results show that wall micro-blowing can simultaneously reduce skin-friction drag and wall thermal load, with the maximum local drag-reduction and heat-reduction rates reaching 17.8% and 7.6%, respectively. Further analysis of the flow-control mechanisms reveals that micro-blowing lifts the mean velocity profile of the turbulent boundary layer, redistributes near-wall low-speed fluid toward the outer region, and is accompanied by enhanced streamwise velocity fluctuations and shear Reynolds stress. Turbulence statistics indicate that micro-blowing intensifies the intermittency of near-wall turbulence, increases the occurrence probability of ejection events, and strengthens the outward transport of low-momentum fluid, which contributes to drag reduction while effectively alleviating wall heat load. These results demonstrate that micro-blowing through small pores has promising potential for simultaneous drag and heat reduction in hypersonic turbulent boundary layers.