Transient Rip Current Dynamics: Laboratory Measurements and Modeling of Surfzone Vorticity

瞬态裂谷流动力学：表面区涡度的实验室测量和建模

• 批准号: 1735460
• 负责人: Melissa Moulton
• 金额: $ 71.7万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-15 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1735460&HistoricalAwards=false
• 关键词: Transient; Rip; Current; Dynamics; Laboratory

The nearshore region, valued as essential intertidal habitat and recreational grounds, is often compromised by pathogens and excess nutrient supply from terrestrial runoff. When an area becomes contaminated, beach closures, ecological disruption, and associated economic losses can result. Understanding the transport of materials throughout the nearshore region can have important implications for ecosystem and human health. Previous studies analyzing cross-shelf exchange suggest that transient rip currents are the dominant mechanism driving exchange between the surf zone and the inner shelf. Evidence also suggests that transient rip currents are generated from the coalescence of surf zone eddies, with short-crested waves serving as the source of rotation. This project will utilize a laboratory and numerical modeling to study the generation and evolution of surf zone eddies to form transient rip currents. The knowledge of mixing and exchange in the nearshore region will be significantly advanced through this study, which will have important implications for the transport of nutrients, larvae, and pollutants. In collaboration with National Oceanic and Atmospheric Administration scientists, simple predictors of transient rip currents will be developed to improve hazard forecasts for a broad range of environments. This is essential information for human safety as rip currents are the leading cause of fatalities and rescues on beaches. A graduate student will gain valuable training and education through involvement in this project. Outreach activities highlighting rip currents will be developed as a part of the O.H. Hinsdale Wave Research Laboratory Outreach Program seeking to broaden participation in Science, Technology, Engineering and Mathematics (STEM).This project seeks to establish a cradle-to-grave picture of the injection of eddies into the surf zone by short-crested wave breaking, coalescence to form larger eddies, and formation of transient rip currents. The overall objective is to determine if the surf zone can be treated as a two-dimensional turbulence box. This study will improve understanding of the dynamics of surf zone eddy generation and evolution leading to transient rip currents and associated cross-shelf exchange by addressing four specific hypotheses: 1) short-crested waves are an important vorticity source at short spatial and temporal scales, 2) smaller eddies coalesce to create bigger eddies, 3) surf zone eddy decay is controlled by bottom friction, and 4) eddies ejected outside of the surf zone onto the shelf deviate from the two-dimensional paradigm. Laboratory experiments will include in situ and remote (stereo visible and infrared) measurements of sea-surface-elevations and velocities for a range of wave heights, periods, and directional spreads. State-of-the-art numerical modeling will be used to guide laboratory sampling, to analyze dynamics for a range of conditions, and to assess the importance of frictional dissipation and three-dimensional circulation properties. If the surf zone can be treated as a forced two-dimensional turbulence box, simplified models with appropriate forcing can be established to advance the understanding of the role of the surf zone in land-to-sea transport.

近岸地区被视为重要的潮间带栖息地和休闲场所，但经常受到病原体和陆地径流过多养分供应的损害。当某个地区受到污染时，可能会导致海滩关闭、生态破坏以及相关的经济损失。了解整个近岸地区的物质运输可能对生态系统和人类健康产生重要影响。先前分析跨陆架交换的研究表明，瞬态离岸流是驱动海浪带和内陆架之间交换的主要机制。证据还表明，瞬态离岸流是由海浪区涡流合并产生的，短波峰是旋转的来源。该项目将利用实验室和数值模型来研究冲浪区涡流的产生和演化，以形成瞬态离岸流。通过这项研究，近岸地区混合和交换的知识将得到显着提高，这将对营养物、幼虫和污染物的运输产生重要影响。将与国家海洋和大气管理局的科学家合作，开发瞬态离岸流的简单预测器，以改进对广泛环境的灾害预测。这是对人类安全至关重要的信息，因为离岸流是造成海滩死亡和救援的主要原因。研究生将通过参与该项目获得宝贵的培训和教育。重点关注离岸流的外展活动将作为 O.H.欣斯代尔波浪研究实验室外展计划旨在扩大对科学、技术、工程和数学 (STEM) 的参与。该项目旨在建立一个从摇篮到坟墓的图景，通过短波峰破碎、合并形成更大的涡流以及瞬态离岸流的形成，将涡流注入冲浪区。总体目标是确定冲浪区是否可以视为二维湍流盒。这项研究将通过解决四个具体假设，提高对导致瞬态离岸流和相关跨陆架交换的海浪区涡流生成和演化动力学的理解：1）短波峰是短时空尺度上的重要涡源，2）较小的涡流合并形成更大的涡流，3）海浪区涡流衰减由底部摩擦力控制，4）涡流被喷射到海浪之外 货架上的区域偏离了二维范式。实验室实验将包括对一系列波高、周期和方向传播的海面高程和速度进行现场和远程（立体可见光和红外）测量。最先进的数值模型将用于指导实验室采样，分析一系列条件下的动力学，并评估摩擦耗散和三维循环特性的重要性。如果可以将冲浪区视为受迫的二维湍流箱，则可以建立具有适当强迫的简化模型，以促进对冲浪区在陆地到海洋传输中的作用的理解。

项目成果

Modeled Three‐Dimensional Currents and Eddies on an Alongshore‐Variable Barred Beach

模拟沿岸可变障碍海滩上的三维水流和涡流

• DOI: 10.1029/2020jc016899
• 发表时间: 2021
• 期刊: Journal of Geophysical Research: Oceans
• 作者: Baker, Christine M.;Moulton, Melissa;Raubenheimer, Britt;Elgar, Steve;Kumar, Nirnimesh
• 通讯作者: Kumar, Nirnimesh