分布式粗糙元对高超声速边界层不稳定性的影响试验

Experiment of influence of distributed roughness elements on hypersonic boundary layer instability

高超声速边界层转捩是空气动力学亟须研究的关键问题之一。飞行器表面的热防护系统会由于高温烧蚀产生宏观分布式粗糙元形貌,但是目前该宏观烧蚀形貌对高超声速边界层内不稳定波演化机制的影响尚不明晰。基于华中科技大学?0.5 m马赫数6 Ludwieg管风洞,利用高频压力传感器(PCB)和红外热像仪等测量手段,重点研究了分布式粗糙元布置位置和宽度对零攻角下7°半张角尖锥模型高超声速边界层不稳定波演化特征和转捩位置的影响。试验结果表明,将分布式粗糙元布置于同步点之前会促进第二模态不稳定波的演化,且越靠近前缘位置粗糙元宽度因素对下游不稳定波演化影响越小;但随其分布位置向下游移动,促进转捩作用减弱,对不稳定波的非线性交互抑制效果更为明显,转捩位置随之后移。

Hypersonic boundary layer transition is one of the key problems in aerodynamics.Macroscopic distributed roughness elements pattern will be produced due to surface high temperature ablation of thermal protection system on the flight vehicle,but its influence on the evolution mechanism of instability waves in the hypersonic boundary layer is not clear now.Based on the∅0.5 m Mach number 6 Ludwieg tube wind tunnel of Huazhong University of Science and Technology,this paper explores the influence of location and width of distributed roughness elements on the evo⁃lution characteristics and transition position of hypersonic boundary layer instability waves of a 7°half-angle sharp cone model at zero angle of attack.PCB sensors and infrared thermography are used.The experimental results show that placing the distributed roughness elements in front of the synchronization point will promote the evolution of the second mode unstable wave;the closer the roughness element is to the leading edge,the smaller the influence of its width on the evolution of downstream instability waves.However,as its distribution position moves downstream,its effect on promoting transition is weakened,and its effect on inhibition of the nonlinear interaction of instability waves is more ob⁃vious,then the transition position moves backward.