柱形汇聚激波作用下单模界面演化的实验研究

Investigation of the Bell-Plesset (BP) and Rayleigh-Taylor (RT) effects on the instability development, which merely exist in the converging circumstance, is significant for understanding the underlying physics of the converging Richtmyer-Meshkov (RM) instability and for guiding practical engineering applications such as the inertial confinement fusion. In this application, we propose to perform a systematic experimental study on the evolution of the single-mode interface subjected to a converging shock wave by an improved semi-annular converging shock tube and an extended soap film technique. The PLIF imaging technique combined with a high-speed schlieren photography is first introduced to the converging RM instability experiment for capturing clear interfacial structures and obtaining various quantitative data including the amplitude variation with time, the gas concentration distribution and the mixing rate. The BP and RT effects on the instability development are inspected in detail based on the experimental results. Also, the perturbation growth regimes as well as the late-stage turbulent mixing characteristics are analyzed. The present project will bring deep insights into the converging RM instability, and provide experimental and theoretical basis for future double-mode and multi-mode RM instability studies.

汇聚Richtmyer-Meshkov(RM)不稳定性中存在着特有的Bell-Plesset(BP)和Rayleigh-Taylor(RT)效应，研究BP(几何收缩)和RT（变速度）效应对扰动发展的影响，探索汇聚空间中扰动发展的内在机理，对理解惯性约束核聚变等工程应用中的复杂界面失稳问题意义重大。本申请基于项目组新设计的半环形汇聚激波管和肥皂膜界面生成技术，率先采用平面激光诱导荧光（PLIF）和高速纹影相结合的方法，详细研究柱形汇聚激波作用下单模气体界面（轻/重和重/轻界面）的演化发展，力求捕捉清晰的界面演化图像，获得扰动振幅随时间变化、气体浓度分布等定量数据，并深入分析BP和RT效应对不稳定性发展的影响，认识汇聚RM不稳定性扰动发展的内在机制和后期的湍流混合特性。本项目研究有望在汇聚RM不稳定性研究方面获得深入认识，为后续双模和多模界面演化研究奠定实验和理论基础。

在本项目支持下，项目组研制了多套不同结构和功能的汇聚激波管设备，生成了初始稳定的柱形汇聚激波，发展了单模/多模/多层界面的生成和控制方法，在此基础上开展了一系列汇聚激波冲击扰动界面的精细实验研究，获得了汇聚激波冲击下不同扰动界面的发展规律，揭示了几何汇聚、界面减速、界面耦合、模态耦合与竞争等效应对不稳定性发展的影响规律，并提出了相应的理论预测模型。这些发现不仅揭示了汇聚激波诱导界面不稳定性的内在机理，为相关理论和数值研究提供可靠的实验数据，而且有助于理解惯性约束核聚变中流体界面失稳的复杂物理过程。相关研究成果已形成 14 篇高质量论文，包括6篇J. Fluid Mech. 论文和4篇Phys. Fluids 论文。