脉冲激光与正激波相互作用过程和减阻机理的实验研究  

EXPERIMENTAL STUDY ON PROCESS AND MECHANISMS OF WAVE DRAG REDUCTION DURING PULSED LASER INTERACTING WITH NORMAL SHOCK

作　　者：王殿恺 文明 王伟东 卿泽旭 Wang Diankai;Wen Ming;Wang Weidong;Qing Zexu(State Key Laboratory of Laser Propulsion and Application,Space Engineeing University,PLA Strategic support Force,Beijing 101416,China)

机构地区：[1]中国人民解放军战略支援部队航天工程大学激光推进及其应用国家重点实验室,北京101416

出　　处：《力学学报》2018年第6期1337-1345,共9页Chinese Journal of Theoretical and Applied Mechanics

基　　金：国家自然科学基金资助项目(11372356)

摘　　要：纳秒脉冲激光具有峰值功率密度高、易于击穿空气形成等离子体这一突出优势,在降低超声速波阻方面具有重要应用价值.以深刻揭示减阻机理为目的,针对激光与正激波相互作用这一基本物理现象开展实验研究.发展高精度纹影技术以测量复杂激波结构,时间分辨率达到30 ns,空间分辨率达到1 mm;搭建快速PIV实验系统以定量测量流场速度和涡量,时间分辨率达到500 ns.探明了激光等离子体引致的球面激波和高温低密度区域特性,揭示了激光等离子体在正激波冲击下的流动特性与演化规律,并结合数值模拟结果阐明了脉冲激光等离子体降低超声速波阻的根本原因.研究表明:激光等离子体引致激波的初始马赫数随着激光能量而增大,形状由水滴形逐渐发展为球面形,传播速度随着时间降低,在50μs后接近于声速;高温低密度区域初始近似于球形,而后从激光入射方向的下游开始失稳,形成尖刺结构;在正激波冲击下,高温低密度区域演化为上下对称的双涡环结构,尺寸随着激光能量而增大.涡的卷吸和逆流可改变飞行器头部激波结构,是流场重构的重要形式,引起飞行器表面压力的大幅降低,是引起超声速飞行器波阻降低的重要机理.Nanosecond pulsed laser has the prominent advantage of high peak power density, so it is easy to break down air to form plasma. It has an important application value in reducing supersonic wave drag. To deeply reveal the mechanisms of wave drag reduction by nanosecond pulsed laser, in this paper, the basic physical phenomenon of the interaction of pulsed laser plasma with a normal shock is studied by experiments. A high resolved schlieren system is developed to reveal the complex wave structures. Time resolution of the schlieren system reaches up to 30 ns, with a space resolution up to 1 mm. A high speed PIV system is applied to measure the velocity and vorticity of the flow field quantificationally. Time resolution of the PIV system reaches up to 500 ns. Features of the spherical shock wave and high temperature area with low density induced by laser plasma are revealed. The flow features and evolution process ofthe laser plasma impacted by shock wave are revealed. Simulated results are adopted to prove the basic reason of super sonic wave drag reduced by pulsed laser plasma. Research results show that： the initial Mach number of the shock wave induced by laser plasma increases with the laser energy increasing, and the shape is gradually developed from the droplet shape to the spherical shape. The propagation velocity decreases with time and is close to the sound velocity after 50 μs. The high temperature with low density region is approximate to sphere at first, and then begins to destabilize from the downstream of the laser incident direction. A sharp spike structure is then formed. Under the impact of the normal shock, the high temperature and low density region evolves into an upper and lower symmetric double vortex ring structure, and the size increases with the laser energy. The entrainment and contra-flow of the vortex can remodel the shape of the shock wave of the nose, which is an important way of flow field remodel. It causes a notable reducing of the surface pressure of the aircraft. It is the key m

关 键 词：超声速 波阻 激光 流动控制 激波管 

分 类 号：V211.1[航空宇航科学与技术—航空宇航推进理论与工程]