Transport Processes in Inland and Coastal Waters

内陆和沿海水域的热量、污染物和沉积物的输送是一个独特而复杂的过程，涉及大范围长度尺度的湍流。湍流的水平长度比流的深度大一到几个数量级。浮力决定了垂直交换，因为界面摩擦和内波的辐射抑制了水平剪切不稳定性。对于足够大尺度的水平长度运动，科里奥利力的虚拟力也是一个决定因素。研究方案的目的是在实地观察的指导下，对这些高度各向异性的过程取得基本的了解。将注意气候变化情景中锋面的加强。该研究方案的一个长期目标是帮助政府和工业界通过“适应”为气候变化的影响做好准备，即通过规划来适应预计会发生的变化。* *我们的研究产生了高引用的出版物，这是理解运输过程的基础。申请人2007年、2008年、2009年、2010年、2011年、2012年发表的Scopus被引频次分别为10、8、20、32、20、32。Chu和Babarutsi（1988； 55篇Scopus引文）对浅层明渠流水平湍流的实验室研究，Ingram和Chu（1987； 67篇Scopus引文）的现场观测，以及Chu、Wu和Khayat（1991； 57篇Scopus引文）对浅层流的水动力稳定性分析现已成为经典，并在第一、第二和第三届浅层流国际研讨会（ISSF 2003、ISSF2008和ISSF2012）上发表了许多后续研究。自那以后，申请人取得了许多进展，包括他最近在水平湍流中发现的波辐射。Pinilla and Chu（2008）和Chu（2010）通过直接数值模拟确定了波辐射的影响，并将其对剪切不稳定性的影响与Froude和Rossby数进行了关联。最重要的是我们发现了一个与地球自转有关的不稳定窗口。在墨西哥湾流和大气的完全非线性模型中，观察到强烈的切变不稳定性在以临界rosby数为中心的狭窄窗口中短暂发生（Pinilla & Chu 2009; Chu 2014）。横过窗口的切变不稳定是强烈的，持续时间短，并且与锋面的增强和可能与气候变化有关的强风暴频率的增加密切相关。**如果没有准确可靠的数值方法的并行发展，水平湍流的研究是不可能的：在过去的六年里，这一直是申请人指导的研究重点，并在Pinilla等人（2010），Tan & Chu (2008, 2012, 2014), Chu & Altai (2012), Chu & Gao（2013）和Ghannadi & Chu（2014）的一系列近期期刊出版物中报道。我们未来五年的研究将集中于改进锋面陡峭梯度的模拟。我们将建立准三维长度尺度划分模型来模拟波浪与湍流之间的相互作用。实验室和实地调查将研究：(a)波辐射的作用；(b)海岸边界层的发展；(c)通过重力分层界面的传热传质过程。实验将在一个新的流动可视化设备中进行，使用视频成像方法来研究波浪和湍流的相互作用。锋面短暂而剧烈的变陡与气候变化情景有关。

The transports of heat, contaminants and sediments in inland and coastal waters are unique and complex processes involving turbulence over a wide range of length scales. The horizontal length scale of turbulence is one to several orders of magnitude greater than is the depth of the flow. Buoyancy determines vertical exchanges, as interfacial friction and the radiation of internal waves suppress the horizontal shear instabilities. For motion of sufficiently large scales of horizontal length, the fictitious force of the Coriolis is also a deciding factor. The purpose of the research programme is to attain a fundamental understanding of these highly anisotropic processes, guided by field observations. Attention will be given to the intensification of fronts in climate-change scenarios. One long-term goal of the research programme is to assist government and industry to prepare for the impacts of climate change through "adaptation" - i.e., by planning to accommodate the changes that are expected to occur. * *Our research has produced highly cited publications that are fundamental to understanding the transport processes. The Scopus citations to the applicant's 2007, 2008, 2009, 2010, 2011, 2012 publications are 10, 8, 20, 32, 20 and 32, respectively. A laboratory study of horizontal turbulence in shallow open-channel flow by Chu and Babarutsi (1988; 55 Scopus citations), a field observation by Ingram and Chu (1987; 67 Scopus citations) and a hydrodynamic stability analysis on the shallow flow by Chu, Wu and Khayat (1991; 57 Scopus citations) are now classics, and have inspired much subsequent research reported in the first, second and third International Symposium on Shallow Flow (ISSF 2003, ISSF2008 and ISSF2012). The applicant has made many advances since, including his recent notable discovery of a wave radiation on horizontal turbulence. Through direct numerical simulations, Pinilla and Chu (2008) and Chu (2010) have determined the effect of the wave radiation, and correlated the effect on shear instabilities with Froude and Rossby numbers. Most significant of all is our discovery of a window of instability related to the Earth's rotation. In fully nonlinear models of the Gulf Stream and of the atmosphere, intense shear instability is observed to occur briefly in a narrow window centered on a critical Rossby number (Pinilla & Chu 2009; Chu 2014). The shear instability across the window is intense, brief in duration, and closely associated with the intensification of the fronts and the increase in the frequency of the severe storms that are likely related to climate change. **The study of horizontal turbulence would not have been possible without the parallel development of accurate and reliable numerical methods: in the past six years, this has been the focus of research supervised by the applicant, and is reported in a series of recent journal publications by Pinilla et al. (2010), Tan & Chu (2008, 2012, 2014), Chu & Altai (2012), Chu & Gao (2013), and Ghannadi & Chu (2014). Our research in the next five years will focus on refining the simulation of the steep gradients across the fronts. We will develop quasi-three-dimensional length-scale-partition model to simulate the interaction between the waves and turbulence. Laboratory and field investigations will study: (a) the role of wave radiation; (b) the development of the coastal boundary layer; and (c) the heat and mass transfer process through gravity-stratified interfaces. The experiments will be conducted in a new flow-visualization facility using a video-imaging method to study the waves and turbulence interaction. The brief and intense steepening of the fronts is to be correlated to the climate-change scenarios.