Flow Past Obstacles in Shallow Water: Wake Structure and Free-Surface Deformation

摘要：浅水流过障碍物：尾流结构和自由面变形本研究的总体目的是对浅水流过水平障碍物时的尾流不稳定性、尾流与自由面变形的耦合以及这些特征对河床载荷的影响有一个基本的认识。穿越洪水河流和海岸线的石油、天然气和输水管道、严重洪水条件下的淹没桥面、河流中的沙丘、尾水中的低水头水力闸门、高速水力排放的能量耗散器以及沿水力坡度控制结构的水流都是产生旋涡结构的构型。这些漩涡通常与浅水层自由表面的扭曲有关，在邻近的床（底壁）存在的情况下。耦合无涡表面不稳定性的后果包括障碍物的稳定和非稳定载荷、冲刷/泥沙输运对河床的载荷、河流或河道的局部共振振荡、由障碍物引起的局部破坏导致的污染物混合以及河流/河道阻力的改变。该项目将通过对漩涡结构和自由表面变形的发生和演变进行定量表征，从而提高对浅水漩涡系统的认识，这两种结构都发生在邻近的地层中。这些贡献将包括障碍物和床的载荷特性，以及控制它们的技术。预计这一见解可以为理论模型和数值技术提供指导，此外，还可以增强工程实践中设计指南的框架。

ABSTRACTCTS-0228110DONALD O. ROCKWELLLEHIGH UNIVERSITY FLOW PAST OBSTACLES IN SHALLOW WATER:WAKE STRUCTURE AND FREE-SURFACE DEFORMATIONThe overall aims of this investigation are to acquire a fundamental understanding of wake instabilities, their coupling with free-surface distortion, and the influence of these features on the bed loading for the case of flow past horizontal obstacles in shallow water. Petroleum, natural gas, and water pipelines across flooded rivers and along coastlines, submerged bridge decks during severe flood conditions, sand dunes in fluvial rivers, low head hydraulic gates in tailwater, energy dissipaters at high-speed hydraulic discharges, and flow along hydraulic grade control structures are among the configurations that generate vortical structures. These vortices typically are linked to distortion of the free-surface of the shallow water layer, in presence of an adjacent bed (bottom wall). Among the consequences of the coupled vortex-free surface instabilities are steady and unsteady loading of the obstacle, loading of the bed with scour/sediment transport, locally resonant oscillations of the river or channel, mixing of pollutants due to local disruptions induced by the obstacle, and alteration of the river/channel resistance.This program will advance knowledge of shallow water vortex systems by yielding quantitative representations of the onset and evolution of vortical structures and free-surface distortion, both of which occur in presence of an adjacent bed. These contributions will include loading characteristics of the obstacle and the bed, and techniques for their control. It is anticipated that this insight can provide guidance for both theoretical models and numerical techniques and, in addition, enhance the framework of design guidelines in engineering practice.