Global conservation of momentum applied to environmental flows

将全局动量守恒原理应用于多相流是一种相对较新的方法，可以理解离散元素移动和消失时会发生什么(参见第1部分中的参考文献)。例如，当蒸汽气泡上升并凝结，或燃料液滴移动并蒸发时，这一点很重要。在元素消失后(从没有应用运动学条件的边界的意义上说)，会留下一个漩涡。动量方法使流动特征的最终状态和旋涡的性质能够与液滴的初始性质或作用在气泡上的力的历史相关。这些想法和概念都经过了实验和理论的检验，线性动量情况下的框架是完整的。本方案的目的是将这一研究扩展到环境流体力学问题。具体地说，这里有两个令人感兴趣的领域：自由表面流动和自行体。量化波浪的动量是众所周知的问题；对于波列来说，讨论动量通量更为常见[1]。应用动量守恒可能有用的一个领域是致密的局部波群或海啸问题。第二个令人感兴趣的领域是自行体，如潜艇。关键问题是它们在不稳定移动时生成的流签名，以及这些签名是否可以被检测到。这两个问题本身都很重要，有些方面可以通过应用全球动量守恒来理解。关键问题是以严格的方式制定概念框架并对这些想法进行实验测试。访问亚利桑那州立大学的重要性被它在国际上领先的两个研究领域所突显：(A)沮丧的海啸动力学。由于2006年12月25日印度洋海啸的偏离效应，海啸研究目前相当活跃。费尔南多教授(亚利桑那州立大学)带领NSF科学事实调查组前往斯里兰卡，其结果已被广泛传播。他们最近关于低沉海啸的实验工作的一个关键方面是使用他们所说的漏水桨来移除低沉海啸的尾巴的能力。实验工作由伦敦大学学院的一名DTA学生进行，他在亚利桑那州立大学呆了3个月。(B)移动潜艇所产生的水下特征。沃罗帕耶夫和他的同事在这一领域特别活跃，在过去几年里发表了六篇关于这个主题的论文。Voropayev是分层和均匀流体中涡旋动力学的领导者，他对由潜艇(模拟为喷流)的非定常直线运动引起的与自由表面相互作用的涡旋特征的发展有了非常一般的理解。利用相似理论和标度分析，Voropayev能够对揭示的表面特征做出一些明确的陈述。

The application of global momentum conservation principles to multiphase flows is a relatively new approach to understand what happens when discrete elements move and disappear (see references in Part 1). This is important, for instance, when vapour bubbles rise and condense, or fuel droplets move and evaporate. After the elements have disappeared (in the sense that there is no boundary on which the kinematic condition is applied), a vortex is left behind. The momentum approach enables the final state of the flow signature and properties of the vortex to related to the initial properties of the droplets or the history of forces acting on the bubbles. These ideas and concepts have been tested experimentally and theoretically, and the framework is complete for the case of linear momentum.The aim of this current proposal is to extend this research to problems in environmental fluids mechanics. Specifically there are two areas of interest here : free surface flows and self-propelled bodies. Quantifying the momentum of wave is known to be fraught with problems; for wave trains it is more usual to discuss momentum flux [1]. One area where applying momentum conservation might be useful is the problem of compact local wave groups or tsunamis. The second area of interest is in self-propelled bodies, such as submarines. The critical issue is the flow signature they generate when they move unsteadily and whether these signatures can be detected. Both these problems are important in their own right and some aspects may be understood by applying global conservation of momentum. The key problem is setting down the conceptual framework in a rigorous manner and to test these ideas experimentally.The importance of visiting Arizona State University is underlined by two research areas in which it leads internationally: (a) Depressed tsunami dynamics. Tsunami research is currently quite active owing to the devistating effect of the Indian Ocean tsunami December 25th 2006. Prof Fernando (ASU) led the NSF scientific fact-finding group to Sri-Lanka and the results have been disseminated quite widely. One of the key aspects of their recent experimental work on depressed tsunamis was the ability to remove the tail of the depressed tsunami using, what they refer to as a leaky paddle . The experimental work was undertaken a DTA student from UCL who stayed at ASU for 3 months. (b) Subsurface signatures generated by moving submarines. Voropayev and his colleagues have been particularly active in this area having published half a dozen papers on the topic in the last few years. Voropayev is a leader in the vortex dynamics in stratified and homogeneous fluids and he has developed a very general understanding of the develop of vortex signatures interacting with the free surface, caused by the unsteady rectilinear motion of a submarine (modelled as a jet). Using similarity theory and scaling analysis enabled Voropayev to make some clear statements about the revealing surface signatures.