Three-dimensional wave breaking

• 成果类型: Article
• 署名作者: McAllister, M. L.; Draycott, S.; Calvert, R.; Davey, T.; Dias, F.; van den Bremer, T. S.
• 署名单位: University of Oxford; University of Manchester; University of Edinburgh; University College Dublin; Universite Paris Saclay; Centre National de la Recherche Scientifique (CNRS); Universite Paris Cite; Delft University of Technology
• 刊物名称: Nature
• ISSN/ISSBN: 0028-5554
• DOI: 10.1038/s41586-024-07886-z
• 发表日期: 2024-09-19
• 页码: 601-607
• 关键词: directionally spread; gravity-waves; deep; DISSIPATION; probability; threshold; state

摘要

Although a ubiquitous natural phenomenon, the onset and subsequent process of surface wave breaking are not fully understood. Breaking affects how steep waves become and drives air-sea exchanges1. Most seminal and state-of-the-art research on breaking is underpinned by the assumption of two-dimensionality, although ocean waves are three dimensional. We present experimental results that assess how three-dimensionality affects breaking, without putting limits on the direction of travel of the waves. We show that the breaking-onset steepness of the most directionally spread case is double that of its unidirectional counterpart. We identify three breaking regimes. As directional spreading increases, horizontally overturning 'travelling-wave breaking' (I), which forms the basis of two-dimensional breaking, is replaced by vertically jetting 'standing-wave breaking' (II). In between, 'travelling-standing-wave breaking' (III) is characterized by the formation of vertical jets along a fast-moving crest. The mechanisms in each regime determine how breaking limits steepness and affects subsequent air-sea exchanges. Unlike in two dimensions, three-dimensional wave-breaking onset does not limit how steep waves may become, and we produce directionally spread waves 80% steeper than at breaking onset and four times steeper than equivalent two-dimensional waves at their breaking onset. Our observations challenge the validity of state-of-the-art methods used to calculate energy dissipation and to design offshore structures in highly directionally spread seas. We conduct experiments in a wave tank and show that waves with realistic three-dimensional spreading can become two times steeper than two-dimensional waves before breaking, with three breaking regimes identified.