Experiments by Invited Researchers


Flow separation in sharp meander bends

Project acronym: HyIII-Hull-03
Name of Group Leader: Dr. Maarten G. Kleinhans, Utrecht University, m.kl
User-Project Title: Flow separation in sharp meander bends
Facility: TES
Proceedings TA Project: Flow separation in sharp meander bends
Data Management Report: There is no Data Management Report available for this project

User-Project Objectives


It is well known that abrupt changes in flow direction may lead to flow separation from boundaries. Flow separation has also been observed in sharp river bends  and the formation of recirculation zones has significant consequences for the morphodynamics of meandering river channels. For example, the presence of a separation zone combined with vortex bar formation decreases the channel width and conveyance capacity and can often lead to localized and focused bank erosion or formation of a muddy counter-point with potential impacts on biota.

The aim of this study is to explore the interrelationships between flow conditions and bend geometry in the causation of flow separation in systematic experiments. The objectives of the project are: (1) determine the overall and detailed flow characteristics including the dimensions of the separated flow zone and turbulence characteristics for a range of flow and bend geometries; (2) investigate the interrelationships between separated flow dimensions and bend geometry; (3) explore the interaction of the separated flow with sediment transport pathways; and (4) disseminate detailed laboratory data and use for model testing. Measurements of three-dimensional flow structure and turbulence under different flow conditions were obtained using a combination of three-dimensional Particle Image Velocimetry, surface Particle Image Velocimetry, acoustic Doppler current profiling and acoustic Doppler velocimetry

Figure 1. Sharp meander bend with gravel bed for fixed bed experiments.

Figure 2. Threads showing flowpaths with flow separation on inner bank (left side of picture).