Collaborative Proposal: Impact of secondary circulation and mixing of estuarine exchange flows.

合作提案：二次循环和河口交换流混合的影响。

• 批准号: 0825876
• 负责人: Arnoldo Valle-Levinson
• 金额: $ 29.13万
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0825876&HistoricalAwards=false
• 关键词: Collaborative; Proposal; Impact; secondary; circulation

Intellectual Merit: This study is the first proposed field effort to quantify the role of secondary circulation in driving the estuarine exchange flow. Although recent numerical studies in a limited estuarine parameter space suggest that the lateral advection is a leading-order term in the subtidal along-channel momentum balance, it has not been confirmed by observations. Observational test of this model result is critical to the field of estuarine oceanography because it raises a fundamental question regarding the validity of the classic theory of estuarine circulation. Numerical and scaling results have suggested that the effects of lateral advection are nearly always balanced by internal stresses so that a simple theory based on the momentum balance between longitudinal pressure gradient and bottom stress provides an accurate prediction for the estuarine residual velocity. The central hypothesis is that the near cancellation between secondary flows and interfacial stress is a manifestation for a possible interaction or feedback between the advective accelerations due to secondary circulation and diffusive momentum transfer due to small-scale turbulent flows. This project will investigate the co-variability between the lateral advection and interfacial stress over the spring-neap tidal cycle and assess their roles in the estuarine exchange flow. We plan to conduct a series of field experiments in the James River estuary, complemented by ROMS (Regional Ocean Modeling System) and LES (Large Eddy Simulations) modeling simulations. Field efforts include moored and shipboard observations as well as dye-release experiments and microstructure profiling. ROMS modeling will focus on the effects of secondary circulation on the estuarine exchange flows in this wide estuary, while LES modeling will examine the interactions and possible coupling between secondary flows and small scale turbulent flows. Results obtained from this project will provide a definitive answer on the role of secondary circulation in estuarine circulation. Broader Impacts: Estuarine dispersion is largely driven by the exchange flow and the ability to predict dispersion is critical in many applied problems such as determining the Maximum Total Daily Load (TMDL) permissible to an estuarine system. More generally, this project will yield much-needed information regarding the circulation and mixing processes in estuaries and help develop state-of-the-art numerical models for simulating estuarine flows, which are required for predicting water quality, contaminant and fish larvae transport. For the field work in the James River, we will involve participation of high school teachers and students from the areas near the estuary. Through the participation of one of the investigator at the University of Florida, this project enhances the involvement of minority groups in science. This project will also provide training to three graduate students and undergraduate interns.

智力优点：这项研究是量化二次循环在驱动河口交换流中的作用的第一个拟议的现场努力。尽管在有限的河口参数空间中的最近数值研究表明，横向对流是沿潮流动量平衡的下潮中的领先项，但尚未通过观察结果证实。该模型结果的观察性测试对河口海洋学领域至关重要，因为它提出了关于河口循环经典理论的有效性的基本问题。数值和缩放结果表明，横向对流的影响几乎总是由内部应力平衡，因此基于纵向压力梯度和底部压力之间的动量平衡的简单理论为河口残留速度提供了准确的预测。中心假设是，次要流与界面应力之间的近来取消是由于次级循环和由于小规模的湍流引起的二次循环和扩散动量传递而产生的相互作用或反馈。该项目将调查弹簧北潮周期的横向对流与界面应力之间的共同变量，并评估其在河口交换流动中的作用。我们计划在詹姆斯河河口进行一系列现场实验，并由ROM（区域海洋建模系统）和LES（大型涡模拟）建模模拟进行补充。现场工作包括停泊和船上观测以及染料释放实验和微观结构分析。 ROM模型将集中于次级循环对这个宽河口中河口交换流的影响，而LES建模将检查次级流和小规模湍流之间的相互作用和可能的耦合。从该项目获得的结果将为二次循环在河口循环中的作用提供明确的答案。更广泛的影响：在许多应用问题中，例如确定河口系统允许的最大总日载（TMDL），河口分散体在很大程度上是由交换流量驱动的，预测分散体的能力至关重要。更一般而言，该项目将产生有关河口中循环和混合过程的急需信息，并有助于开发最新的数值模型，以模拟河口流，这些模型是预测水质，污染物和鱼类幼虫运输所必需的。对于詹姆斯河（James River）的现场工作，我们将参与河口附近地区的高中教师和学生的参与。通过佛罗里达大学的一名研究人员的参与，该项目增强了少数群体参与科学的参与。该项目还将为三名研究生和本科实习生提供培训。