激波聚焦反射的实验和数值研究

 采用高速摄影技术和数值模拟方法，对入射激波在两种不同形状的抛物形反射器表面聚焦和反射的过程进行了研究，得到了激波聚焦反射过程的波系结构的实验阴影照片和数值计算结果，两者符合得很好。对激波聚焦形成的气体动力学焦点的特性进行了分析，结果表明，入射激波在两种反射器反射后聚焦所形成的气体动力学焦点均是由三波点在轴心处的会聚所导致的，气体动力学焦点位于相应的反射器壁面的几何焦点附近。不同的反射器中，激波聚焦前后的波系结构也不同，对较浅的反射器，入射激波反射前在反射器壁面形成了弓形激波，反射之后需要相对较长的时间完成聚焦，形成聚焦反射激波之后弓形激波仍未相交；对较深的反射器，入射激波反射后在更短的时间内聚焦，聚焦时弓形激波已经相交，聚焦反射激波之后的流场波系结构更加复杂。

Experimental and Numerical Investigation of Shock Wave Focusing and Reflection

The incident shock wave focusing and reflection on the two parabolic reflectors were studied by means of high speed photograph technique and numerical simulation method.The experimental shadow photographs and computational density contours were obtained,and the good agreements between the experimental and computational results were presented.The properties of the gasdynamic focus,formed by shock wave focusing,were analyzed.The results show that for both reflectors studied the gasdynamic focus is formed by the collision of two triple points at the axis,and that this focus is located in the vicinity of the corresponding geometrical focus.The shock-shock structures after shock wave focusing are different for the two reflectors.For the shallow reflector,the bow shock waves form on the surface of reflector before the reflection of incident shock wave;it takes long time to complete the focusing once incident shock wave reflects from reflector;the bow shock waves do not intersect each other during the shock wave focusing and reflection.For the deep reflector,it takes short time to complete the focusing,the bow shock waves have intersected during the shock wave focusing and reflector,and this process leads to the more complex shock-shock structure.