Understanding Rip Currents: The Multi-scale Interactions of Waves, Currents and Morphology

0756271 Yu这项研究研究了碎波区波生流的复杂动力学和水文形态动力学系统的多尺度动力学，最终将在近岸环境中进行更好的预测。碎波驱动的碎波带流是近海岸输送、混合和分散水、沉积物和污染物的主要媒介。这些强烈影响海岸侵蚀，因此海岸漫顶和洪水，以及水质。深入了解这些海流的动力学特征，对沿海环境、经济和生态系统的发展和保护具有重要意义。裂流被广泛认为是危险的海滩危害，占美国冲浪区救援的80%。理论上的理解，离岸生成机制还不令人满意，特别是在海滩缺乏沿岸的变化。最近的研究主要集中在形态动力学不稳定性（流体和可侵蚀海床之间的反馈），没有仔细考虑波浪和水流之间的完全动力学相互作用。这有效地模拟了由形态演变控制的慢时间尺度，抑制了流体动力学过程的较快时间尺度。为了解决各种时间尺度的重要性，PI计划通过耦合波流相互作用引起的流体动力学不稳定性（Yu，2006）和形态动力学，彻底研究波、流和形态之间的多尺度相互作用。该研究计划将包括扩展的线性分析的流体动力学不稳定性，导致rip电流，数值研究的非线性开发的rip电流，并与慢尺度morphodynamics耦合。将通过与现有观测结果的直接和间接比较来验证建模。需要改进开发可靠的预测工具，这些工具对基于科学的规划、决策和减缓战略至关重要。 在气候变化情景中，海岸演变已成为一个更加令人关切的问题，因为全球海平面上升增加了风暴潮的可能性，漫顶和洪水泛滥的风险也增加了。计划的研究支持研究生课程的发展。除了培养两名研究生外，还将通过PI努力开发海岸工程和环境流体力学研究生课程来促进研究和教育。更广泛的教育影响也预计通过推广计划的PI的合作者，包括国家气象局威尔明顿，北卡罗来纳州海洋赠款和北卡罗来纳州大学，海岸研究所。

0756271 YuThis research studies the complex dynamics of surf zone wave-induced currents and the multi-scale dynamics of the hydro-morphodynamic system that will eventually lead to better predictions in the nearshore environment. Surf zone currents, driven by breaking waves, are the primary agents to transport, mix and disperse water, sediments and pollutants in the near shore. These strongly influence coastal erosion, hence coastal overtopping and flooding, and water quality. Better understanding of the dynamics of these currents is important to the development and protection of coastal environment, economy and ecosystem. Rip currents are widely known as dangerous beach hazards and account for 80% of surf zone rescues in the USA. Theoretical understanding of rip generation mechanisms has not been satisfactory, in particular on beaches lacking alongshore variability. Recent studies have mostly focused on morphodynamic instabilities (feedback between fluid and erodible seabed), not carefully considering the fully dynamical interaction between waves and currents. This effectively models only the slow time scale controlled by the morphology evolution, suppressing the faster time scale of the hydrodynamic processes. To address the significance of the various time scales, the PI plans to thoroughly investigate the multi-scale interactions among waves, currents and morphology, by coupling the hydrodynamic instability due to wave-current interaction (Yu, 2006) and the morphodynamics. The research program will include extended linear analysis of the hydrodynamics instability leading to rip currents, numerical study of the nonlinear developed rip currents, and the coupling with slow-scale morphodynamics. The modeling will be validated through direct and indirect comparisons with available observations. Improvements are needed for development of reliable predictive tools essential to science-based planning, decision-making and mitigation strategies. Coastal evolution has become even more of a concern within the climate change scenarios, as the rise of global sea levels increases the likelihood of storm surges as do the risks of overtopping and flooding. The planned research supports the development of a graduate program. In addition to training two graduate students, research and education will also be fostered through the PI's efforts to develop a graduate curriculum in Coastal Engineering and Environmental Fluid Mechanics. A broader educational impact is also expected through the outreach programs of the PI's collaborators, including the National Weather Service Wilmington, NC Sea Grant and University of North Carolina, Coastal Studies Institute.