Surfzone Vorticity

面带涡度

• 批准号: 2341381
• 负责人: Steve Elgar
• 金额: $ 73.89万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-06-01 至 2026-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2341381&HistoricalAwards=false
• 关键词: Surfzone; Vorticity

Breaking waves dissipate energy while transferring momentum that forces water in the direction of wave propagation. In the shallow water of the surf zone the time-averaged wave-driven forcing raises water levels near the shoreline and, in the case of obliquely incident waves, drives alongshore currents. The resulting circulation patterns include a rich field of eddies and vortices. Surfzone eddies have been hypothesized to be generated by instabilities of sheared alongshore currents, by wave-group modulations of the sea surface, by the ends of breaking waves, and by currents interacting with complex bathymetry. This project will address these hypotheses with a unique suite of high spatial resolution estimates of currents from remote sensing and in situ sensors obtained during prior field studies that include a wide range of wave conditions and bathymetries.Existing extensive field observations of surfzone waves, circulation patterns, and underlying bathymetry will be used to test hypotheses about surfzone vorticity that were derived from numerical studies. These hypotheses include: (1) on an alongshore variable seafloor, the dominant spatial scales of surfzone vorticity depend on spatial scales of the underlying bathymetry, and these large-scale eddies are tied to the seafloor inhomogeneities; (2) small spatial-scale vorticity also depends on the vorticity injected into the water column at the ends of breaking waves, which increases with the directional spread of the wave field; (3) during energetic conditions, the momentum of alongshore currents can overcome forces (such as bathymetry-induced pressure gradients) that cause complex circulation patterns, resulting in alongshore-uniform flow with significantly reduced large-scale vorticity. Although the data used here are from a specific field site, the wide range of wave and bathymetric conditions observed over a decade allows development of a surfzone vorticity climatology that will be applicable at many locations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

破碎波会消散能量，同时传递动量，迫使水沿波传播方向移动。在冲浪区的浅水中，时间平均波浪驱动力提高了海岸线附近的水位，并且在波浪倾斜入射的情况下，驱动沿岸流。由此产生的环流模式包括丰富的涡流和涡流场。据推测，海带涡流是由沿岸剪切流的不稳定性、海面的波群调制、破碎波的末端以及与复杂测深相互​​作用的海流产生的。该项目将通过在先前的现场研究中获得的遥感和原位传感器获得的一套独特的高空间分辨率水流估计来解决这些假设，其中包括广泛的波浪条件和水深测量。现有对海浪、环流模式的广泛现场观测，并且基础测深将用于检验从数值研究中得出的有关海面区涡度的假设。这些假设包括：（1）在沿海可变海底，海面区涡度的主要空间尺度取决于底层测深的空间尺度，而这些大尺度涡流与海底不均匀性有关； (2) 小空间尺度涡度还取决于破碎波末端注入水柱的涡度，涡度随着波场的定向扩展而增大； （3）在能量条件下，沿岸流的动量可以克服引起复杂环流模式的力（例如测深引起的压力梯度），从而产生沿岸均匀流，并显着降低大尺度涡度。尽管这里使用的数据来自特定的现场站点，但十多年来观察到的广泛的波浪和测深条件允许开发适用于许多地点的表面区涡度气候学。该奖项反映了 NSF 的法定使命，并被认为是值得的通过使用基金会的智力优势和更广泛的影响审查标准进行评估来获得支持。