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You are here : eLibrary : IAHR World Congress Proceedings : 34th Congress - Brisbane (2011) : THEME 5: Environmental Hydraulics and Hydrology : Turbulence and fine sediment suspension in accelerating and decelerating open-channel flow
Turbulence and fine sediment suspension in accelerating and decelerating open-channel flow
Author : Fereshteh Bagherimiyab1 and Ulrich Lemmin2
This experimental investigation describes the effect of suspended sediment concentration and turbulence modulation in unsteady (first accelerating, then decelerating) flow by combining an acoustic Doppler and imaging method (ADVP) with an optical method (PTV) for suspended sediment particle tracking. Quasi-instantaneous profiles of velocity and sediment concentration were taken simultaneously and co-located, resolving turbulence scales. An event structure in suspension is seen by both methods. During the final phase of the accelerating flow range, fine sediment suspension from the bed started in bursts and rapidly created nearly stationary ripples. Thereafter, vortices, shedding from the ripple crests, produced most of the sedimentsuspension in events. In that state, flow deceleration had less obvious effects on particle motion. PTV velocity vectors varied in speed and orientation, but were organized in large coherent packets, mainly in the near bed layers, supporting the concept that coherent structure events contribute to sediment suspension in unsteady flow.
File Size : 581,824 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 34th Congress - Brisbane (2011)
Article : THEME 5: Environmental Hydraulics and Hydrology
Date Published : 01/07/2011
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