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research article

Topographic steering, flow recirculation, velocity redistribution, and bed topography in sharp meander bends

Blanckaert, K.  
2010
Water Resources Research

The bed topography and associated flow field are investigated in a laboratory configuration with parameters that are representative for sharp natural meander bends. Zones of inward mass transport are characterized by a quasi-linear transverse bed profile, whereas zones of outward mass transport, induced by pronounced curvature variations, are characterized by a quasi-horizontal shallow point bar at the inside of the bend, a deep pool at the outside, and an increase in overall cross-sectional area. These quasi-bilinear bed profiles can be attributed to the curvature-induced secondary flow that is confined to the pool. Topographic steering, mainly due to mass conservation, concentrates the major part of the discharge over the deepest zones of the bend. But the pattern of depth-averaged velocities, which is relevant with respect to the development of the bed topography, does not show maximum values over the deepest zones. A term-by-term analysis of the depth-averaged streamwise momentum equation reveals that the water surface gradient is the principal mechanism with respect to flow velocity redistribution, although inertia and secondary flow are also processes of dominant order of magnitude. A required condition for the occurrence of adverse pressure gradients and flow recirculation due to planform curvature variations is established. A different type of flow recirculation, due to a subtle feedback between the flow and the bed topography, occurs over the point bar. The neglect of the influence of vertical velocities impinging on the bed in models for sediment transport is identified as a major shortcoming in the modeling of the morphodynamics of meandering river channels.

  • Details
  • Metrics
Type
research article
DOI
10.1029/2009WR008303
Web of Science ID

WOS:000281634600002

Author(s)
Blanckaert, K.  
Date Issued

2010

Publisher

American Geophysical Union

Published in
Water Resources Research
Volume

46

Issue

9

Article Number

W09506

Subjects

Open-Channel Bends

•

Curved Open Channels

•

Sediment Transport

•

River Bends

•

Turbulence Measurements

•

Alluvial Channels

•

Secondary Flow

•

Model

•

Simulation

•

Separation

Note

[748]

Editorial or Peer reviewed

NON-REVIEWED

Written at

EPFL

EPFL units
PL-LCH  
Available on Infoscience
December 23, 2010
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/62478
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