Modelling Extreme Free-Surface Flows: applications to breaking waves, wave-structure and wave-vessel interactions

拟议的研究涉及极端自由表面流动的描述，并应用于深水近海和浅水沿海地区。这项工作将涉及发展一种新的数值模型，适合于描述大的表面水波及其与固定结构和浮动船只的相互作用。连接这些流动的关键特征将是波浪破碎的发生；包括水面的破裂，空气的夹带和高度湍流区域的快速发展。从实际的角度来看，这种流动极其重要，因为它们与最高（极限）水面高度、最大水粒子速度和最大施加流体载荷有关。因此，它们与各种海洋结构和船舶的设计直接相关。为了模拟这样的流动，并以此提供更好的物理理解，新的数值模型将结合两种非常不同的建模程序的优点：在波浪破碎开始之前应用的边界元方法和用于破碎和破碎后流体流动的光滑粒子流体力学。通过将这些程序结合起来，所提出的方法将寻求创建一个能够描述大范围自由表面流动的稳健和准确的模型；特别关注波浪结构和波浪-容器相互作用的那些方面，这些方面对设计至关重要，无法用现有的解决程序来描述。模型的预测将根据新的实验室观测结果进行验证。这将涉及使用按比例的物理模型试验，并将考虑各种实际重要的流体流动，包括：(i)破碎波，包括大规模倾覆波和溢出波；（ii）波浪-结构相互作用中的高度非线性效应，包括高频波散射、垂直喷射（流体向上投射到非常高的高度，造成甲板上的波浪载荷）以及波浪对垂直柱和甲板结构的撞击；（iii）波浪与船只的相互作用，特别是绿水泛滥和大冲击力的发生。在解决这些问题的过程中，结合实验和数值研究将寻求对这些事件发生的时间和原因提供新的物理理解，评估它们的实际含义，并确定如何在工程实践中最好地建模。所提出的工作涉及流体力学的广泛问题，特别是在海洋结构的有效设计和安全运行方面的应用。提案中包含了三个主要工业从业者的直接支持。该项目还将与可再生能源行业相关。由于人们对将海上风力发电场选址在大风和大浪活动地区很感兴趣，这种结构非常容易受到大规模波浪破碎和相关冲击力的影响。航运业也将从该项目中受益：新模型提供信息，以改进船舶的设计和/或安全操作，提高生存能力，并在油轮的情况下，限制大规模环境影响和破坏的可能性。最后，该作品还具有真正的多学科贡献，超越了沿海/近海/肚脐建筑的界限，从某种意义上说，水面的破裂（特别是空气的夹带）对一般的海气相互作用有影响，特别是质量交换（二氧化碳吸收）。这些问题对于研究海洋表面转移过程的海洋学家来说是至关重要的，也是气候变化模拟的一个关键因素。

The proposed research concerns the description of extreme free-surface flows with applications in both deep water offshore and the shallow water coastal locations. The work will involve the development of a new numerical model appropriate to the description of large surface water waves and their interaction with both fixed structures and floating vessels. The key feature linking these flows will be the occurrence of wave breaking; involving the break-up of the water surface, the entrainment of air and the rapid development of areas of highly turbulent flow. From a practical perspective such flows are extremely important because they are associated with the highest (limiting) water surface elevations, the largest water particle velocities and the maximum applied fluid loads. As a result, they are directly relevant to the design of all manner of marine structures and vessels.In order to simulate such flows, and in so doing provide improved physical understanding, the new numerical model will combine the advantages of two very different modelling procedures: a Boundary Element Method applied before the onset of wave breaking and Smooth Particle Hydrodynamics applied to the breaking and post-breaking fluid flow. By combining these procedures the proposed method will seek to create a robust and accurate model capable of describing a wide range of free-surface flows; particular attention being paid to those aspects of wave-structure and wave-vessel interactions that are critical for design and cannot be described by existing solution procedures.The model predictions will be validated against new laboratory observations. This will involve the use of scaled physical model tests and will consider a wide range of practically important fluid flows including:(i) Breaking waves, including both large-scale over-turning and spilling waves;(ii) Highly nonlinear effects in wave-structure interaction, including high-frequency wave scattering, vertical jetting where fluid is projected upwards to very high elevations creating wave-in-deck loads, and wave slamming on both vertical columns and the deck structure;(iii) Wave-vessel interactions, particularly the occurrence of green water inundation and large impact forces.In tackling these problems, the combined experimental and numerical studies will seek to provide new physical understanding of when and why these events occur, to assess their practical implications and to identify how they can best be modelled in engineering practice.The proposed work is relevant to a wide range of problems in fluid mechanics, with particular application to the effective design and safe operation of marine structures. Direct support from three key industrial practitioners is incorporated within the proposal. The project will also be relevant to the renewable energy industry. With interest in locating offshore wind farms in areas of high wind and therefore large wave activity, such structures are very susceptible to large-scale wave breaking and the associated impact forces. The shipping industry will also benefit from this project: the new model providing information to improve the design and/or safe operation of vessels to both increase survivability and, in the case of oil tankers, limit the potential for large-scale environmental impact and damage. Finally, the work also has a truly multi-disciplinary contribution, beyond the coastal/offshore/navel architecture boundaries, in the sense that the break-up of the water surface (specifically the entrainment of air) has implications for air-sea interactions in general, and mass exchange (CO2 absorption) in particular. Such issues are of fundamental importance to oceanographers studying the transfer processes at the ocean surface and contribute a key element to climate change modelling.