Network: Wave-flow interactions

在许多环境和工业应用中遇到的流体的动力学是流动运动和波传播的复杂混合物。流动和波浪可以以各种方式相互作用：流动可以产生波浪，就像人们熟悉的湍流产生的噪音的例子所证明的那样，但波浪也会产生水流运动，就像海面波迫使沿岸水流的情况一样。了解流与波相互作用的本质是流体力学中的一个重要问题，有着广泛的应用。这也是一个非常困难的问题：首先，什么是运动流体中的波的定义并不直接。波流相互作用的研究目前在英国很活跃：几个小组在这个问题的不同方面开展工作，特别是在地球物理流的背景下。他们考虑不同类型的流动和波浪，并使用不同的技术(分析、数值、实验)。然而，这些小组研究的问题背后的数学模型有许多共性，如果能够启动小组之间的合作将是非常有益的。这就是拟议的网络的目标。通过年度会议和小型研讨会，它将促进研究人员与互补专业知识之间的互动，从而有效地应对当前的挑战。首先是波浪和水流的分离。这里所寻求的既是适当的数学定义，也是识别流体运动的哪些分量可以被视为流动和波的实用方法。第二个问题与水流自发产生的波浪有关。当考虑到比非色散波更复杂的情况时，这在很大程度上仍然是开放的。第三个问题是通过波浪产生强健的平均气流，这种类型控制着大气环流的某一部分。这里的挑战将是超越目前的理论，通常局限于对称平均流，并对耗散和非耗散相互作用进行建模。第四个问题是表面波和洋流之间的相互作用，并将其应用于反常波和海啸波传播的模拟。这四个问题将得到其他问题的补充，这些问题将在网络成员的互动中出现。

The dynamics of the fluids encountered in many environmental and industrial applications is a complicated mixture of flow motion and wave propagation. Flows and waves can interact in a variety of ways: flows can generate waves, as the familiar example of turbulence-generated noise demonstrates, but waves also generate flow motion, as in the case of along-shore currents forced by sea-surface waves. Understanding the nature of the interaction between flows and waves is a problem of central importance in fluid dynamics, with a broad range of applications. It is also a very difficult problem: for a start, the very definition of what is a wave in a moving fluid is not straighforward. Research on wave-flow interactions is currently buoyant in the UK: several groups work on different aspects of the problem, especially in the context of geophysical flows. They consider different types of flows and waves and use different techniques (analytical, numerical, experimental). However, there are many commonalities in the mathematical models underlying the problems these groups study, and it would be highly beneficial if collaborations between the groups could be initiated. This is the aim of the proposed Network. Through yearly meetings and small-scale workshops, it will stimulate interactions between researchers with complementary expertises, so that current challenges can be tackled efficiently.Four problems have been identified to start collaborative work. A first is the separation between waves and flow. Here what will be sought are both suitable mathematical definitions and practical means of identifying which components of fluid motion can be regarded as flow and as waves. A second problem concerns the spontaneous generation of waves by flow. This remains largely open when situations more complex than that of non-dispersive waves are considered. A third problem is the generation of robust mean flows by waves, of the type that controls some part of the atmospheric circulation. The challenge here will be to go beyong the current theory, often limited to symmetric mean flows, and to model both dissipative and non-dissipative interactions. A fourth problem is that of the interaction between surface waves and ocean currents, with applications to the modelling of freak waves and tsunami-wave propagation. These four problems with be complemented by others which will emerge from the interactions of the Network members.