Collaborative Research: Rip Current Dynamics in a Complex Beach Environment

在过去的三十年里，实地实验主要是在平面形状相对简单的海滩上进行的（直线和平行等高线）。这些观测结果被用来验证深度平均波驱动流模型。 在很大程度上，当地的垂直流结构在沿岸流和回流的海滩缺乏沿岸的变化。 然而，直的和平行的底部轮廓，或简单的海滩平面形状不是一个稳定的形态动力学海滩状态，与复杂的形态是规范。这激发了在复杂海滩上进行实验的动机。裂流、瞬时裂流和碎波带涡旋与碎波带中的重力波（入射涌浪和亚重力波）共存，但由于缺乏对复杂地貌海滩系统的全面现场测量和数值模型验证，它们的重要性和动力学耦合尚未得到认识。在这个项目中，我们将参与欧洲的一个实地实验，旨在了解与裂流形态相关的近岸环流。 计划于2008年春季在法国特吕克维尔特海滩进行一次多机构和国际实地试验。该海滩具有充满活力的波浪气候、强烈的潮汐调制和典型的复杂海滩地貌，包括新月形沙坝、裂槽和具有山脊和水道系统的潮间带。科学目标是通过观测和先进的数值模拟来研究低频裂流脉动的近岸混合、平均流型、沉积物输运和水深耦合。嵌入在跨和沿岸固定的仪器阵列，新的拉格朗日观测使用廉价的冲浪区漂移舰队将提供重要的空间地图的流通模式。密集的欧拉和拉格朗日观测沿着数值模拟工作将用于评估近岸动量和能量的跨岸和沿岸分布，影响沉积模式和运输，以及海洋这一高度利用段的水团混合。研究的更广泛影响包括预测位置，持续性和撕裂流的强度，以确保游泳者的安全，了解近岸混合，模拟污染物的扩散，预测海岸线和沙丘侵蚀。这种类型的海滩平面形状比以前已经研究过的任何一种都要复杂，因此，在世界任何地方获得的现有数据集中，拟议的数据将是独一无二的。在更广泛的传授中，这项工作将为多达六名研究生提供动手研究和论文机会。

Over the past three decades, field experiments have been performed primarily on beaches with relatively simple planforms (straight and parallel contours). These observations were used to verify depth-averaged wave-driven flow models. To a large extent, the local vertical flow structure in alongshore currents and undertow is understood on beaches lacking alongshore variability. However, straight and parallel bottom contours, or simple beach planforms are not a stable morphodynamic beach state, with complex morphology being the norm. This has motivated experiments on complex beaches. Rip currents, transient rip currents, and surf zone eddies co-exist with gravity waves (incident sea-swell and infragravity) in the surf zone, yet their importance and dynamic coupling have gone unrecognized owing to a lack of comprehensive field measurements and numerical model verification on complex morphologic beach systems. For this project, we will participate in a European field experiment aimed at understanding nearshore circulation associated with rip current morphology. A multi-institutional and international field experiment is planned for the spring of 2008 at Truc Vert Beach, France. This beach features an energetic wave climate, strong tidal modulation, and a typically complex beach planform composed of crescentic bars, rip channels, and an inter-tidal zone with ridge and runnel systems. The scientific objectives are to examine the nearshore mixing, mean flow patterns, sediment transport, and bathymetric coupling of low frequency rip current pulsations through observations and advance numerical modeling. Imbedded in cross- and alongshore fixed instrument arrays, new Lagrangian observations using a fleet of inexpensive surf zone drifters will provide vital spatial maps of circulation patterns. The dense Eulerian and Lagrangian observations along with the numerical modeling efforts will be used to evaluate the cross- and alongshore distribution of momentum and energy in the nearshore, the influence sedimentation patterns and transport, and the mixing of water masses in this heavily utilized segment of the ocean.The broader impacts of the research include predicting location, persistence, and strength of rip currents for swimmer safety, understanding nearshore mixing, modeling dispersion of pollutants, and anticipating shoreline and dune erosion. This type of beach planform is more complex than any that has been previously studied in a comprehensive fashion, and thus the proposed data will be unique among available data sets obtained anywhere in the world. Among the broader imparts, this effort will provide hands-on research and thesis opportunities for up to six graduate students.