Collaborative Research: Ocean Wave Dissipation through Breaking and Bubble Generation

该项目涉及海洋表面波浪的破碎以及在此过程中产生的气泡。 波浪破碎是海洋表面湍流和混合的重要来源，包括海洋和大气之间气体和热量的湍流交换。 波浪破碎也对海上船舶的航行和安全通行构成危险。 关键问题是“波浪破碎时损失了多少能量？". 这种损失的能量既是准确预报海浪的重要参数，也是规定海洋-大气交换的重要参数。 最近的研究表明，在波浪破碎过程中产生的气泡的数量和大小是控制能量耗散的关键，从而破碎的强度。 该项目将利用实地观测和计算机模型来验证这种依赖性，并将其应用于改进波浪预报和海洋-大气耦合。拟议的工作将支持博士后研究人员，并有助于公众宣传，为华盛顿大学的年度发现日活动做出具体贡献，该活动涉及来自地区K-12学校的10，000名学生。该项目的技术方法是用自由漂移的浮标测量开阔海洋中的波浪破碎，这些浮标配备有运动传感器，湍流剖面仪，和摄像机来记录气泡所提出的工作建立在最近的结果，使用表面波仪器浮子跟踪（SWIFT）漂移测量湍流耗散率下破碎波和基于VOF（流体体积）欧拉欧拉多分散双流体模型来模拟两相泡状流。以前的结果表明，泡沫耗散可能是一个越来越大的部分，在高海况的总波破碎耗散。将对该项目中进行的测量进行分析，以确定气泡的时间演变，以及与单个破碎波相关的湍流和运动。这些数据将被用来测试最近的配方，缩放总耗散与时间积分的气泡羽流体积。此外，将评估一种相关的公式，该公式将气泡羽流深度与海洋表面可见的泡沫斑块面积进行缩放。改进后一种公式将能够估计羽流体积并远程推断消散情况。推导出的公式将与其他耗散估计值进行比较，其中包括：菲利普斯破碎波峰分布，平衡风输入，和湍流耗散的现场测量。拟议的工作还将审查不连续性的影响和稀疏抽样实地观察的后果。这些测量结果将与高分辨率，双流体模型模拟的破碎过程进行比较。这种方法将使破碎波条件的更全面的调查和评估的观测结果的固有稀疏性。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

This project concerns the breaking of waves at the ocean surface and the bubbles generated during that process. Wave breaking is an important source of turbulence and mixing at the ocean surface, including the turbulent exchange of gasses and heat between the ocean and the atmosphere. Wave breaking is also a hazard to navigation and safe passage for vessels at sea. The key question is "how much energy is lost when waves break?". This lost energy is both an important parameter for accurate wave forecasts and for prescribing ocean-atmosphere exchange. Recent work has suggested that the quantity and size of bubbles generated during wave breaking are the key controls on the energy dissipation and thus the strength of breaking. This project will use field observations and computer models to verify this dependence, with application to improve wave forecasting and ocean-atmosphere coupling. The proposed work will support a postdoctoral researcher and contribute to public outreach with specific contributions to the annual Discovery Days event at the University of Washington, that reaches 10,000 students from regional K-12 schools.The technical approach of the project is to measure wave breaking in the open ocean with freely drifting buoys that are equipped with motion sensors, turbulence profilers, and cameras for bubble recording. The proposed work builds on recent results using the Surface Wave Instrument Float with Tracking (SWIFT) drifters to measure the turbulent dissipation rate beneath breaking waves and a VOF-based (volume of fluid) Eulerian-Eulerian polydisperse two-fluid model to simulate the two-phase bubbly flow. Previous results suggest that dissipation by bubbles may be an increasingly large fraction of the total wave breaking dissipation during high sea states. The measurements to be carried in this project will be analyzed to determine the time evolution of the bubbles, as well as the turbulence and motion associated with individual breaking waves. The data will be used to test a recent formulation that scales the total dissipation with the time integral of the bubble plume volume. Further, a related formulation that scales bubble plume depth with the area of foam patches visible at the ocean surface will be evaluated. Improvement of the latter formulation will allow estimates of plume volume and infer dissipation remotely. The formulation derived will be compared with other estimates for dissipation, which include: the Phillips breaking crest distribution, equilibrium wind input, and in situ measurements of turbulent dissipation. The proposed work will also examine the effects of intermittence and the consequences of sparsely sampled field observations. These measurements will be compared with the high resolution, two-fluid model simulations of the breaking process. This approach will enable a more complete investigation of breaking wave conditions and an assessment of the inherent sparseness of the observations.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.