Rip Current Dynamics in a Complex Beach Environment

该项目将补充海军研究生院和特拉华大学的合作努力，作为欧洲野外实验的一部分，通过观察和数值模拟，在具有大水深变化的海滩上，在湍流、入射波、次重力波、极低频和平均时间尺度上检查三维近岸流动动力学。实地试验计划于2008年春季在法国波尔多附近大西洋沿岸的Truc Vert海滩进行。这个海滩的特点是充满活力的波浪气候，强烈的潮汐调制，一个典型的复杂平台，有新月形的沙洲，裂口通道和带山脊和河道的潮间带。将采用最先进的数值模拟技术来设计和优化由共置压力和速度传感器、压力传感器、ADCP？S，并在野外实验前安装了一个底边界层仪器。原位仪器在初始部署后很难移动，因此实验前计算是必不可少的。在现场实验中，还将采用数值模拟的方法优化冲浪带漂船的部署，以绘制离岸流系统的表面速度场。为此，数值模型将使用拉格朗日/欧拉混合的近地表速度场描述。这些计算将有助于了解初始漂船部署的最佳位置，以捕获我们研究中感兴趣的近岸环流。这些最佳位置受（变化的）波浪和潮汐条件的影响，可以很容易地通过数值模拟来评估。更广泛的影响：拟议研究的影响包括预测离岸流的位置、持续时间和强度，以保证游泳者的安全，模拟沉积物和污染物的分散（包括来自雨水排放等点源和来自农业径流等分布源），以及预测海岸线和沙丘侵蚀。Truc Vert的海滩平台比迄今为止研究过的任何海滩平台都要复杂。因此，它对高能波条件下三维水动力响应的建模提出了巨大的挑战，所获得的数据集在世界上任何地方的可用数据集中都是独一无二的。最后，参与现场实验将为数值建模者提供第一手经验，并获得测量数据，以便将来进行模型数据比较。

This project will supplement a collaborative effort with the Naval Postgraduate School and the University of Delaware as part of a European field experiment to examine through observations and numerical modeling the three dimensional nearshore flow dynamics at the turbulent, incident wave, infragravity wave, very low frequency and mean times scales on a beach with large bathymetric variability. The field experiment is planned for the spring of 2008 and will be conducted at Truc Vert Beach on the Atlantic coast near Bordeaux, France. This beach features an energetic wave climate, strong tidal modulation, and a typically complex planform with crescentic bars, rip channels and an inter-tidal zone with ridges and runnels. State of the art numerical modeling will be used to design and optimize the in-situ field arrays composed of coherent co-located pressure and velocity sensors, pressure sensors, ADCP?s, and a bottom boundary layer instruments prior to the field experiment. The in-situ instruments are very difficult to move after the initial deployment and therefore pre-experiment computations are essential. Numerical modeling will also be used during the field experiment to optimize the deployment of surf zone drifters to map the surface velocity field of the rip current systems. To that end the numerical model will use a mixed Lagrangian/Eulerian description of the near surface velocity field. These computations will give insight in the optimal location of the initial drifter deployments to capture nearshore circulations that are of interest to our research. These optimal locations are subject to the (changing) wave and tidal conditions which can be easily assessed with the numerical modeling. Broader Impacts: The impacts of the proposed research include predicting location, persistence, and strength of rip currents for swimmer safety, modeling dispersion of sediment and pollutants (both from point sources such as storm drain discharge and from distributed sources such as agricultural runoff) and anticipating shore line and dune erosion. The beach planform at Truc Vert is more complex than any that has been studied up to date in a comprehensive fashion. As such it poses a formidable challenge in the modeling of the three dimensional hydrodynamic response during energetic wave conditions and the data set to be obtained would be unique among available data sets anywhere in the world. Finally, participation in the field experiment will give first hand experience to a numerical modeler with the acquired measurement data allowing for future model-data comparisons.