Experimental Investigation about the second-mode waves in hypersonic boundary layer over a cone at small angle of attack

Abstract An experiment investigating the second-mode instability on the sharp cone with a small angle of attack has been conducted. The fine structure in the boundary layer has been visualized by the Nano-tracer-based Planar Laser Scattering(NPLS) technique. The “rope-like” second-mode waves are found to still be the dominant structures before the transition of the boundary layer at 1 ° angle of attack and the leeside-forward and windside-aft of the transition have also been verified. The propagation velocity of the second-mode waves on the leeward side increases obviously as the disturbance evolving downstream. The development of the disturbance has been analyzed through the wall-fluctuation pressure. The amplification of amplitude is nonmonotonic along the circumferential direction and the M-factor patterns indicated that the disturbance development is delayed in three indentation regions: 55 ° ⩽ φ ⩽ 65 ° , 85 ° ⩽ φ ⩽ 95 ° and 130 ° ⩽ φ ⩽ 140 ° .