Collaborative Research: Quantifying Stratified Turbulence in Estuaries

理解强分层中的湍流混合是流体动力学中一个长期存在的基本问题。本研究的目的是确定大梯度理查德森数下河口混合的机制，并在此条件下测试湍流参数化。这一领域的大多数高质量数据来自实验室测量和直接数值模拟。湍流通量和耗散率的实地测量对于在地球物理相关尺度上理解湍流是必不可少的。河口是分层湍流的极好实验室，因为它们结合了强分层和强潮汐强迫。测量、模拟和分析将阐明分层湍流和河口动力学。在两个河口进行了测量，预计混合是由截然不同的机制驱动的。用于感应湍流的移动阵列（MAST）测量将由三维雷诺平均数值模拟补充，这将把测量与更大规模的河口动力学联系起来，并允许对湍流参数化进行评估。MAST是一种新型的野外仪器平台，能够以前所未有的空间和时间分辨率解决关键的湍流量。这些目标将通过在固定模式和航行模式下进行的具有高空间和时间分辨率的湍流通量、耗散率和长度尺度的MAST测量来检验，从而允许长时间序列测量和空间变异性的量化。三维数值模型作为河口和海岸环境的管理工具，发挥着越来越重要的作用。更广泛的影响还将包括一个明确的组成部分，以传达本研究的含义，以改进用于跨学科科学和管理应用的河口和沿海环流模型中的湍流关闭参数化。

Understanding turbulent mixing in strong stratification is a longstanding fundamental problem in fluid dynamics. The objectives of the proposed study are to determine the mechanisms responsible for estuarine mixing at large gradient Richardson number and to test turbulence parameterizations in this regime. Most high-quality data in this regime have resulted from laboratory measurements and direct numerical simulations. Field measurements of turbulent fluxes and dissipation rates are essential to understand turbulence at geophysically relevant scales. Estuaries are excellent laboratories for stratified turbulence because they combine strong stratification with strong tidal forcing. The measurements, simulations, and analyses will elucidate both stratified turbulence and estuarine dynamics. Measurements are conducted in two estuaries where the mixing is expected to be driven by distinctly different mechanisms. The Mobile Array for Sensing Turbulence (MAST) measurements will be complemented by three-dimensional Reynolds-averaged numerical simulations, which will place the measurements in context with the larger scale estuarine dynamics and permit evaluations of the turbulence parameterizations. The MAST is a new field instrument platform that can resolve key turbulent quantities with unprecedented spatial and temporal resolution. The objectives will be examined with MAST measurements of turbulent fluxes, dissipation rates, and length scales with high spatial and temporal resolution in fixed and underway modes, thus permitting both long time-series measurements and quantification of spatial variability. Three-dimensional numerical models play an increasingly important role as management tools in estuarine and coastal environments. The broader also impacts will include an explicit component to communicate the implications of this study to improve the turbulence-closure parameterizations in estuarine and coastal circulation models for interdisciplinary science and management applications.