反射激波作用下两种重气柱界面不稳定性实验研究

摘要

The evolutions of the Richtmyer-Meshkov instability of two kinds of membrane-less heavy gas cylinder (SF6 and argon),under reshock condition with a specific reflected dis-tance,are experimentally studied in a horizontal square shock tube.Based on the jet technique, SF6 and argon gas cylinders are generated respectively to study the effect of Atwood number on the development of the Richtmyer-Meshkov instability.For the visualization of the flow,the tested gases are mixed with glycol droplets which are generated by the fog generator.Illuminated by a continuous laser sheet with a width of 80mm and a thickness of 1 mm,the interface mor-phologies after incident shock and reshock impact are captured in a single test run with the help of the high speed camera.The results show that different evolving rates and interface morphologies before and after reshock are observed for SF6 and argon gas cylinders due to the different Atwood numbers.For the same reflected end wall,the visible two reversed vortex rings are generated for the SF6 gas cylinder after the incident shock passage,which are not apparently observed for the argon gas cylinder because of less vorticity deposition on the interface.Moreover,after the re-shock impact,secondary vortex rings which have reversed rotating directions to the original vor-tex rings are quickly generated in the SF6 gas cylinder and dominate the flow field at the later stage,becoming the primary feature of the flow.However,in the argon gas cylinder,the second-ary vortex rings,though generated with opposite directions of rotation to the original ones,are not fully developed all the time due to the smaller Atwood number that results in less production of reversed baroclinic vorticity on the argon interface.The present results illustrate the pronounced influence of the Atwood number on the development of the Richtmyer-Meshkov instability.%在水平方形激波管中对两种无膜重气柱界面（分别是SF6和氩气）在反射激波作用下的不稳定性发展进行了实验研究。气柱界面采用射流技术形成，实验采用连续激光片光源照射流场，乙二醇作为示踪粒子，并用高速摄像机对流场进行拍摄，获得了入射激波以及反射激波共同作用下，两种不同气柱界面的演化过程。实验结果表明，两种气柱的Atwood数不同，界面演化速率不同，反射激波到达前后的界面形态不同。SF6气柱在入射激波作用下会产生两个比较明显的反向的涡环结构，而氩气柱界面上由于产生的涡量较少，涡环结构并不明显。在反射激波作用下，SF6气柱界面会出现明显的次级涡对，而且次级涡对的旋转方向与初始涡环结构的旋转方向相反。对于氩气柱而言，在反射激波作用下虽然也产生了与初始涡环方向相反的次级涡对，但次级涡对始终未充分发展。这是因为反射激波作用时氩气柱界面的Atwood数较小导致氩气柱界面上产生的反向涡量较少。实验结果充分表明了气体Atwood数对界面不稳定性的发展起到了较大的影响。