Surfzone Energy Cascades

Surfzone 能量级联

• 批准号: 1948137
• 负责人: Steve Elgar
• 金额: $ 97.84万
• 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: 2020
• 资助国家: 美国
• 起止时间: 2020-03-01 至 2025-02-28
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1948137&HistoricalAwards=false
• 关键词: Surfzone; Energy; Cascades

Rotational currents with order 0.1 m/s velocities and periods of about 30 minutes have been observed in many surf zone environments and for a wide range of conditions. These low-frequency surf zone eddies provide a mechanism for cross-shore dispersion and exchange of material between the shore and the inner continental shelf. This study tests the hypothesis that low-frequency surf zone currents may be the result of energy transfer from breaking waves. Existing data from an extensive two-dimensional array of wave and current sensors will be analyzed to investigate the inverse energy cascade to lower frequencies. Due to limitations in the spatial scales resolvable by the existing data, new data will be collected through the deployment of an alongshore array of wave and current sensors in the surf zone. The sensor deployment will occur during a multi-agency-funded field project to take place in 2020, leveraging significant infrastructure and ancillary measurements. In addition to understanding the contribution of these low frequency oscillations to material exchange between the surf zone and the coastal ocean, the study will also address the need for exposure of future scientists and professional engineers in field data collection and analysis. The project will provide students and young coastal professionals field data collection experiences and 1-week long workshops in analyzing field observations. In addition, the research will form part of the dissertation of an MIT-WHOI PhD student advised by the PIs.There are several hypotheses for the generation of low-frequency surf zone motions, including instabilities of mean currents (shear waves), slow modulations of the incident wave field (wave groups), and nonlinear energy transfers (breaking waves). The wide range of observed wave conditions in existing field data sets, combined with new observations will allow separation and isolation of these mechanisms. Preliminary analyses of surf zone observations suggest that some statistics of the low-frequency current field are consistent with the expectations of a two-dimensional inverse energy cascade. Based on preliminary results, two hypotheses have been formulated and will be investigated as part of this project: (1) vortical energy with spatial scales of a few meters injected into the surf zone at the ends of high frequency (50 to 300 mHz) breaking wind waves is transferred to low-frequency ( 4 mHz) surf zone currents via a two-dimensional inverse cascade, and (2) enstrophy (the integral of vorticity squared) is transferred from breaking-wave-generated vorticity to smaller-scale, higher-frequency motions via a two-dimensional forward cascade. The spatial scale for which the inverse and forward cascades intersect is an indication of the spatial scale of the injected vorticity.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.

在许多海浪带环境和广泛的条件下，观测到了速度为0.1m/S、周期约为30分钟的旋流。这些低频的海浪带旋涡为海岸和内大陆架之间的跨岸扩散和物质交换提供了一种机制。这项研究验证了这样一种假设，即低频海浪带电流可能是破碎波能量转移的结果。我们将分析来自波流传感器的大量二维阵列的现有数据，以研究向更低频率的反向能量级联。由于现有数据可分辨的空间尺度有限，将通过在冲浪区部署近岸海浪和海流传感器阵列来收集新的数据。传感器的部署将在2020年由多个机构资助的实地项目期间进行，利用重要的基础设施和辅助测量。除了了解这些低频振荡对海浪带和沿海海洋之间的物质交换的贡献外，这项研究还将解决未来科学家和专业工程师在实地数据收集和分析方面暴露的需要。该项目将为学生和年轻的沿海专业人员提供实地数据收集经验和为期一周的实地观测分析讲习班。此外，这项研究将成为PIS建议的麻省理工学院-WHOI博士生论文的一部分。关于海浪低频运动的产生，有几个假设，包括平均流的不稳定性(剪切波)，入射波场的缓慢调制(波群)，以及非线性能量转移(破碎波)。现有现场数据集中广泛的观测到的波动条件，再加上新的观测结果，将使这些机制得以分离和隔离。对SURF区观测的初步分析表明，低频电流场的一些统计数据与二维逆能量级联的预期一致。根据初步结果，提出了两个假设，并将作为该项目的一部分进行研究：(1)在高频(50~300 MHz)破碎风浪末端注入海浪带的几米尺度的涡能通过二维逆级联转移到低频(4 MHz)海浪带流中；(2)拟能(涡度平方积分)通过二维正向叶栅从破碎波产生的涡度转移到较小尺度的高频运动。反向和正向叶栅相交的空间尺度是注入漩涡的空间尺度的指示。这一奖项反映了NSF的法定使命，并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，被认为值得支持。

项目成果

Coastal topography and hydrogeology control critical groundwater gradients and potential beach surface instability during storm surges

沿海地形和水文地质控制风暴潮期间的关键地下水梯度和潜在的海滩表面不稳定

• DOI: 10.5194/hess-26-5987-2022
• 发表时间: 2022
• 期刊: Hydrology and Earth System Sciences
• 影响因子: 6.3
• 作者: Paldor, Anner;Stark, Nina;Florence, Matthew;Raubenheimer, Britt;Elgar, Steve;Housego, Rachel;Frederiks, Ryan S.;Michael, Holly A.
• 通讯作者: Michael, Holly A.

Observations of two-dimensional turbulence in the surfzone

表面区二维湍流的观测

• DOI: 10.1063/5.0159170
• 发表时间: 2023
• 期刊: Physics of Fluids
• 影响因子: 4.6
• 作者: Elgar, Steve;Dooley, Ciara;Gorrell, Levi;Raubenheimer, Britt
• 通讯作者: Raubenheimer, Britt

Field Evidence of Inverse Energy Cascades in the Surfzone

冲浪区逆能量级联的现场证据

• DOI: 10.1175/jpo-d-19-0327.1
• 发表时间: 2020
• 期刊: Journal of Physical Oceanography
• 影响因子: 3.5
• 作者: Elgar, Steve;Raubenheimer, Britt
• 通讯作者: Raubenheimer, Britt

Nearshore Vertical Pore Pressure Gradients and Onshore Sediment Transport under Tropical Storm Forcing

• DOI: 10.1061/(asce)ww.1943-5460.0000723
• 发表时间: 2022-11
• 期刊: Journal of Waterway, Port, Coastal, and Ocean Engineering
• 作者: M. Florence;N. Stark;B. Raubenheimer;S. Elgar

Field Observations of the Evolution of Plunging‐Wave Shapes

暴跌演变的现场观察——波浪形状

• DOI: 10.1029/2021gl093664
• 发表时间: 2021
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: O'Dea, Annika;Brodie, Katherine;Elgar, Steve
• 通讯作者: Elgar, Steve