Unsteady wave phenomena in high-speed compressible flows

提出的大范围研究计划的统一主题是高速可压缩流中的非定常波现象。这里的重点是高速，这使得所研究的现象的压缩效应和波状性质突出，以及本质的流动非定常，这对研究人员来说是一个挑战，与相关的稳态气体动力流动相比，研究得很少。从物理数学的角度来看，所有这些流体现象都是用所谓的双曲守恒定律系统来描述的，这使得在数学模型和计算机代码的同一框架内处理这些乍一看没有太多共同之处的现象成为可能。**本着这种精神，该计划包括四个主要研究方向：(I)本质上不稳定的曲面激波反射的基本原理和不同类型反射之间的转换：与这些现象的物理机制和实验观察的解释有关的一些问题最近成为吸引许多研究人员的热点和有争议的话题；拟议的项目旨在为辩论作出关键和决定性的贡献；（二）下一代高超声速吸气式发动机（超燃冲压发动机）进气道启动：本课题前期提出的基于非定常效应（如膈膜破裂）的新型进气道启动技术，将在更现实的模型上进一步研究，以寻找其实际实施的途径；对广泛使用的船外溢出技术进行深入的研究和优化；（三）在两个应用领域遇到的复杂介质中的冲击波现象：用于轨道碎片撞击卫星地基试验的内爆驱动超高速发射装置，以及冲击波在各种医疗应用中使用的激光脉冲能量沉积在液体中产生的冲击波传播和空化泡动力学；（四）非线性磁声学：非均匀介质中波相位共轭（声信号的时间反转）的建模，在医学治疗和诊断、无损检测和流量计量中有许多应用。**该计划的主要研究工具将是由首席研究员早些时候开发的一套高分辨率和高效的流动求解器。为了更准确、高效、可靠地处理上述问题，计划对这些数值方法和代码进行进一步的阐述。此外，首席研究员与上述四个研究方向（澳大利亚、加拿大、法国、日本）的实验诊断领域的世界领导者建立了非常密切的合作关系，他们将提供他们的实验数据，并进行首席研究员建议和设计的实验。这种世界性的合作，符合我们全球化时代的真正精神，将确保所有三种调查模式-理论，实验和数值-在拟议的研究计划中得到最有效的结合。**主要成果预计将是在所选研究领域的基础性和实践性发现，并通过档案期刊的评审出版物提交给研究和工程界；广泛培养研究生/本科生，在许多方面营造独特的研究环境，并进一步开发激波流动非定常气体动力学通用计算机代码，这些代码已经被世界上许多研究人员使用，无疑将为今后的研究事业和其成果的实际应用奠定坚实的基础。

The unifying theme of the proposed wide-scope research program is unsteady wave phenomena in high speed compressible flows. The key points here are high velocities, which make compressibility effects and wave-like nature of the phenomena under study prominent, and essential flow unsteadiness, which challenges researchers and is much less studied as compared to relevant steady gasdynamic flows. From the physico-mathematical point of view all these fluid phenomena are described by so-called hyperbolic systems of conservation laws, making it possible to treat, within the same framework of mathematical models and computer codes, the phenomena which at first superficial glance do not have much in common. **In this spirit, the program encompasses four major research directions: (I) Fundamentals of essentially unsteady shock wave reflections from curved surfaces and transitions between different types of reflection: a number of issues related to physical mechanisms of these phenomena and interpretations of experimental observations have recently become a hot and contentious topic attracting many researchers; the proposed project is aimed at making crucial and decisive contributions to the debate; (II) Starting of air intakes for next-generation hypersonic air-breathing engines (scramjets): novel intake starting techniques based on unsteady effects (e.g., diaphragm-rupture induced) proposed earlier by the principal investigator will be further studied with more realistic models aiming at finding the ways of their practical implementation; an in-depth study and optimization of the widely used overboard spillage technique will be undertaken as well; (III) Shock wave phenomena in complex media as encountered in two application areas: the implosion-driven hypervelocity launcher for ground-based testing of orbital debris impact on satellites, and the shock wave propagation and cavitation bubble dynamics generated by laser pulse energy depositions in liquids as used in various medical applications of shock waves; (IV) Nonlinear magneto-acoustics: modelling of waves phase conjugation (time-reversal of acoustic signals) in heterogeneous media which has many applications in medical treatments and diagnostics, non-destructive testing and flow metrology. **The main research tool of the program will be the set of high-resolution and efficient flow solvers developed earlier by the principal investigator. These numerical methods and codes are planned to be further elaborated for more accurate, efficient and reliable treatment of the above problems. Furthermore, the principal investigator forged very close collaborative ties with, arguably, world leaders in experimental diagnostics for the four research directions mentioned above (from Australia, Canada, France, Japan), who would supply their experimental data and additionally perform experiments suggested and designed by the principal investigator. Such worldwide collaboration, in the true spirit of our era of globalization, would ensure that all three modes of investigation - theoretical, experimental and numerical - are used in the most effective combination within the proposed research program. **The major outcomes are expected to be discoveries of both fundamental and practical nature in the chosen research areas delivered to research and engineering community via refereed publications in archival journals; extensive training of graduate/undergraduate students in stimulating and in many aspects unique research environment, and further development of general computer codes for unsteady gasdynamics of shocked flows, which are already in use by many researchers worldwide and would undoubtedly serve as a solid base for future research undertakings and practical applications of their results.