Laboratory Simulation of Field Measurements of the Bottom Boundary Layer

靠近洋底的湍流区具有丰富的动力过程。该区域可以方便地认为是由重叠的湍流底边界层（TBBL）和湍流底混合层（TBML）组成。由于沿等深线流动的普遍性质及其相对简单，最近关于沿边界湍流区域的许多研究都是在这些条件下进行的；例如，沿着海岸线和山脊流动。在过去的几十年里，现场实验，加上理论和数值模拟的努力，加深了我们对这个边界区域的理解。然而，我们的知识还存在空白。例如，有必要(i)对TBBL和TBML之间的关系有更好的理解，（ii）对湍流的Ekman层阻滞有更多的信息，因为它是在某些现场项目中观察到的，而不是在其他项目中。（二）关于双对数边界层是否存在存在争议；（四）对海洋湍流边界层的各种野外实测资料进行整理和巩固，形成一个统一的整体是有必要的。该项目的智力价值在于有可能清楚地证明，使用湍流的实验室模拟可以或不能定量地模拟海洋边界层。所考虑的物理系统是存在背景旋转的分层流体沿等深线流动。提出的研究的第一个目标是证明海洋的TBBL可以在实验室中使用一个足够大的旋转平台来模拟。为了实现这一目标，实验室模拟将直接与现有的实地数据进行比较，这些数据来自于沿布莱克外脊的北大西洋深西边界流的深水流研究，以及沿北加州大陆架的等深线流的冬季和夏季。这些与海洋数据的直接比较也将阐明TBBL和TBML之间的关系。二是将底剪应力、边界层深度、地转流与底剪应力夹角等数据根据系统外部参数进行概化；这些参数包括斜率伯格数，从实验开始的归一化时间和定义表面粗糙度的参数。相似性需要证明，正如在许多工程流动中，随着雷诺数变大，流动特性与雷诺数无关，这种情况称为雷诺数相似性。更广泛的影响：如果该项目能够成功地根据一套清晰的参数（其中许多参数可以远程测量）定义底部边界层的总体特征，它将对海洋学子学科的范围产生广泛的影响。此外，该项目将支持国际科学，并为美国和法国学生提供在国际氛围中互动的机会。

The turbulent region near the ocean floor is rich in dynamical processes. This region can be conveniently thought of as consisting of overlapping turbulent bottom boundary layers (TBBL) and turbulent bottom mixed layers (TBML). Because of the ubiquitous nature of flows along isobaths and their relative simplicity, much of the recent research on turbulent regions along boundaries has been performed under these conditions; e.g., flows along coastlines and ridges. Field experiments, coupled with theoretical and numerical modeling efforts during the past several decades have sharpened our understanding of this boundary region. There are gaps in our knowledge, however. There is a need, for example, to (i) have an improved understanding of the relation between the TBBL and the TBML, (ii) to have more information on Ekman layer arrest for turbulent flows because it is observed in certain field programs and not in others, (ii) there is controversy on the occurrence of double log boundary layers and (iv) it is desirable tobetter organize and consolidate the knowledge gained from various field measurements on oceanic turbulent boundary layers into some sort of unified whole. The intellectual merit of the project lies in the possibility of demonstrating clearly that laboratory simulations employing turbulence can or cannot quantitatively simulate oceanic boundary layers. The physical system considered is the along isobath flow of a stratified fluid in the presence of background rotation. The first objective of the proposed research is to show that the ocean's TBBL can be simulated in the laboratory using a sufficiently large rotating platform. To accomplish this, the laboratory simulations are to be compared directly with existing field data from studies of the deep water flow of the North Atlantic Deep Western Boundary Current along the Blake Outer Ridge and the winter and summer-time along isobath currents along the Northern California Shelf. These direct comparisons with ocean data will also shed light on the relation between the TBBL and the TBML. The second objective is to generalize data on the bottom shear stress, boundary layer depth and angle between the geostrophic flow and the bottom shear stress in terms of the external parameters of the system; these include the slope Burger number, the normalized time from the beginning of the experiment and parameters defining the surface roughness. Similarity will require the proof that, as in many engineering flows that as the Reynolds number becomes large, the flow characteristics become independent of the Reynolds number, a condition termed Reynolds number similarity.Broader impacts: This project will have broad impact on the range of oceanographic sub-disciplines if it can be successful in defining gross features of the bottom boundary layer in terms of a clear set of parameters, many of which can be measured remotely. Additionally the project will support international science and provide US and French students opportunities to interact in an international atmosphere.