弱激波冲击无膜重气柱和气帘界面的实验研究

研制了一个改进的激波管设备,对马赫数为1.2的弱激波冲击作用下空气中SF6气柱和气帘界面的演变过程进行了初步的实验研究。通过设计激波管实验段、烟雾发生器、气体箱、进气吸气系统和激波管尾段,控制混合气体中SF6的峰值浓度和初始气流速度,建立了稳定、可重复的无膜气柱和气帘初始界面形成技术。利用高速摄影技术,在水平面内观测了气柱和气帘的初始界面图像,沿垂直方向观测了界面RM(Richtmyer-Meshkov)不稳定性的演变过程。气柱演变图像显示了典型的对涡结构,气帘演变图像显示了早期的多蘑菇形结构和后期的相邻波长干扰效应。图像后处理表明,气柱的高度和宽度、气帘的宽度均随时间单调增加,且宽度比高度增加快得多。从二维涡量动力学方程出发,对图像中涡的演变过程进行了初步解释。

Experimental Study on the Membraneless Heavy Gas Cylinder and Gas Curtain Interfaces Impacted by a Weak Shock Wave

A modified shock tube apparatus has been developed in order to experimentally investigate the evolution process of a sulfur hexafluoride gas cylinder and gas curtain surrounded by air when impacted by a shock wave with a Mach number of 1.2. By designing the test section, the fog generator, the gas chamber, the suction system and the end section, and controlling the sulfur hexafluoride peak concentration in the mixing gas and the initial vertical flow velocity, we developed a steady and repeatable technique to generate gas cylinder and gas curtain interfaces. Using high-speed camera, the initial interface images in the horizontal plane are obtained, and the developing photographs of dynamic Richtmyer-Meshkov (RM) instability in the vertical direction are also recorded. The gas cylinder evolution photographs exhibit typical vortex pair structure, and the gas curtain evolution images show multi-mushroom structure in the early stage and interfering with neighboring wavelength in the later stage. The height and width of the gas cylinder and the width of the gas curtain increase monotonically with time. Moreover the width increases faster than the height. The evolution mechanism of vortex is explained preliminarily, using two-dimensional vorticity dynamic equation.