Collaborative Research: Coastal Form Drag and Eddies

合作研究：海岸形成阻力和涡流的智力价值这项研究将探索“形式阻力”的物理学，以及它对沿海地区潮汐能量消散的重要性。形状阻力是流体通过障碍物的压力差所产生的总阻力的一部分，在这种情况下是粗糙的地形。形状阻力通常与大的、连贯的流动特征的产生有关，例如潮汐涡流和内波。因此，这项研究部分集中在控制这些涡流和波动的产生和衰减的物理机制上。这类阻力的重要性已被视为深海中潮汐能量耗散的主要候选因素，而在沿海海洋中，更经典的阻力类型，即底部边界层摩擦，被认为更重要。然而，PI们最近对华盛顿州普吉特湾三树点海角的潮汐流动进行的研究表明，形状阻力是从该海湾地区的潮汐中提取能量的主要机制，至少是20倍。他们将继续这项工作，总体目标是预测水流在任何沿海地区的复杂地形上流动时将经历的净阻力(和能量损失)。此外，PI还试图了解分层流体中倾斜涡流的动力学和消散机制，这是潮汐消散的关键过程。目前的研究有两个主要目标。首先是对现有观测数据进行进一步的分析，结合新的数值模拟和实验室实验，以确定倾斜涡势涡旋的演化机制。第二个部分是形状阻力的数值研究，目的是发展一种实用的方法：(I)在复杂航道形状下的形状阻力计算；(Ii)在数值模型中的形状阻力的参数化。更广泛的影响这项研究将有助于提高沿海数值环流模式的预报技能，增加我们对未解决的粗糙地形的影响的了解。数值模型是用于从概念上理解海洋和预测实际管理决策结果的重要工具。通过这样的使用，模型精度的提高将产生普遍的科学和社会效益。这项研究还将通过两名研究生和三名本科生的参与来促进教育。

ABSTRACTOCE0425893: Collaborative Research: Coastal Form Drag and EddiesIntellectual Merit This study will explore the physics of "form drag," and its importance to the dissipation of tidal energy in coastal regions. Form drag is that part of the total drag experienced by a fluid flow that arises from pressure differences across an obstacle, in this case rough topography. Form drag is typically associated with the generation of large, coherent flow features, such as tidal eddies and internal waves. The study therefore focuses in part on the physical mechanisms governing the creation and decay of these eddies and waves. The importance of this type of drag has come to be seen as a leading candidate for the dissipation of tidal energy in the deep ocean, whereas in the coastal ocean the more classical type of drag, bottom boundary layer friction, is assumed to be of greater importance. However, the PIs' recent work on tidal flow past the Three Tree Point headland in Puget Sound, WA demonstrated that form drag was, by at least a factor of 20, the dominant mechanism extracting energy from the tides in that region of the Sound. They will continue that line of work, with the overall goal of predicting the net drag (and loss of energy) a current will experience when flowing over the complex topography of any coastal region. In addition the PIs seek to understand the dynamics and dissipation mechanisms of tilted eddies in a stratified fluid, which are key processes in tidal dissipation. The current study has two main objectives. The first is to perform further analysis of existing observations, along with new numerical simulations and lab experiments, to determine the tilted eddy potential vorticity evolution mechanisms. The second component is a numerical investigation of form drag with the goal of developing a practical method of (i) its calculation in complex channel shapes, and (ii) its parameterization in numerical models. Broader Impacts This study will help to improve the predictive skill of coastal numerical circulation models, by increasing our understanding of the effects of unresolved rough topography. Numerical models are important tools used both for conceptual understanding of the ocean and for predicting outcomes of practical management decisions. Improvements to model accuracy will have general scientific and societal benefits through such uses. This study will also contribute to education through the involvement of two graduate students and three undergraduates.