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

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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.