汇聚激波动力学特性及其诱导的RM不稳定性实验研究

The investigation on the dynamic characteristics of the converging shock waves in a shock tube is proposed in the project. Through the restriction of the thin needles, fluid interface with different shapes can be formed and the RM instability phenomena of the interface induced by cylindrical converging shock waves is investigated by the high-speed schlieren and continuous laser-sheet techniques. It is expected to obtain the dynamic phenomena of the converging shock reflection or refraction at a solid wall or a fluid interface, and to observe the wave propagation and the interface movement during the shock-interface interaction, as well as the quantitative information of the flow field, such as the velocity and vorticity fields. Accroding to this investigation, the dynamic characteristics of the converging shock wave will be understood; and a new interface formation method will be developed to generate fluid interface with different shapes. Then the interface evolution after the converging shock impact is obtained and the influence of the initial interface shape on the RM instability development is established. Due to the extremely high pressure and temperature achieved at the converging center, the converging shock wave possesses great potential in many appications, such as the inertial confinement fusion and the astrophysics. Moreover, the RM instability under converging shock wave condition involves complicated multiscale and strongly nonlinear physical problems, which is also quite significant in these applications. Baroclinic mechanism is one of the most prominent reasons that result in the development of RM instability, which is closely related to the intial shock shape and the interface shape. It is, therefore, quite necessary to explore the RM instability of the interface with different shapes induced by converging shock waves.

本申请提出在激波管中研究汇聚激波动力学特性；通过细针约束等方式形成各种形状界面并采用高速纹影技术及激光切片技术研究汇聚激波诱导下不同形状界面的RM不稳定性现象。力求获得汇聚激波在壁面和流体界面上的反射和折射现象；获得激波-界面相互作用过程中波系结构和界面发展，以及流场的速度场、涡量场等定量信息。通过本项研究，了解汇聚激波动力学特性；发展一种新的界面生成技术，得到不同形状界面在汇聚激波作用下的发展演化，建立不同界面形状对RM不稳定性发展的影响的数据库。汇聚激波由于能够在其中心得到极高的温度和压力，在ICF、天体物理等领域都有重要的应用价值。而汇聚激波诱导下的RM不稳定性涉及到复杂多尺度的物理问题在这些工程应用中也有重大的研究背景。斜压机制是RM不稳定性产生和发展的一个重要因素，与激波形状和初始界面形状密切相关，因此研究汇聚激波作用于不同形状气体界面的RM不稳定性发展是十分必要的。

本项目开展了汇聚激波动力学特性以及汇聚激波和平面激波作用下不同形状气体界面演化的实验与数值研究，取得的创新性进展总结如下：.汇聚激波方面：.1. 研究了汇聚激波在斜劈/界面上非定常反射/折射现象，发现了新的波系转变现象，获得了与准定常条件不同的反射/折射规律，探索了流场的汇聚效应对反射/折射规律的影响；.2. 开展了汇聚激波诱导下单模界面演化的实验研究，获得了界面演化的定量结果，发现Rayleigh-Taylor效应会降低扰动增长率，甚至导致界面发生提前反相；.3. 开展了扰动汇聚激波诱导无扰动界面演化的实验研究，获得了与平面激波不同的扰动汇聚激波的传播规律，发现了扰动激波诱导界面失稳与经典界面失稳机制的不同.平面激波方面：.1．.开展了平面激波诱导下不同顶角V形界面的演化规律，探讨了振幅波长比对振幅增长率发展的影响，发现线性增长率随振幅波长比的增长并非单调函数，为已有的数值结果提供了实验依据；.2．开展了平面激波诱导下三维单模/气柱界面演化规律研究，发现界面主曲率相同/相反的三维界面会促进/抑制扰动的增长，获得了界面曲率对扰动增长的影响规律；.总之，该项目按计划完成了预定内容，研究成果将有助于凝聚研究方向，形成较好的人才队伍。通过本项目研究，获得了汇聚激波动力学特性以及汇聚激波诱导的界面扰动发展规律，揭示了激波作用下不同形状界面演化的物理规律及内在机理，为惯性约束核聚变等实际应用提供了重要的指导。