Secondary flow in sharp open-channel bends

Secondary currents are a characteristic feature of flow in open-channel bends. Besides the classical helical motion (centre-region cell), a weaker and smaller counter-rotating circulation cell (outer-bank cell) is often observed near the outer bank, which is believed to play an important role in bank erosion processes. The mechanisms underlying...

Turbulence characteristics in sharp open-channel bends

In spite of its importance, little is known about the turbulence characteristics in open-channel bends. This paper reports on an experimental investigation of turbulence in one cross section of an open-channel bend. Typical flow features are a bicellular pattern of cross-stream circulation (secondary flow) and a turbulence activity in the outer...

Flow and bathymetry in sharp open-channel bends: Experiments and predictions

This paper focuses on experiments and simulations conducted in very sharp open-channel bends with flat and equilibrium bathymetry, corresponding to the initial and final phases of the erosion and deposition processes, respectively. The study of flow in curved open bends is relevant for flow in natural river configurations, as most river reaches...

Large-eddy simulation of a mildly curved open-channel flow

After validation with experimental data, large-eddy simulation (LES) is used to study in detail the open-channel flow through a curved flume. Based on the LES results, the present paper addresses four issues. Firstly, features of the complex bicellular pattern of the secondary flow, occurring in curved open-channel flows, and its origin are...

Simultaneous measurements with 3D PIV and Acoustic Doppler Velocity Profiler

Simultaneous velocity measurements were taken using Particle Image Velocimetry (PIV) and an Acoustic Doppler Velocity Profiler (ADVP) in a sharp open-channel bend with an immobile gravel bed. The PIV measures 3D velocity vectors in a vertical plane (~40cm x 20cm) at a frequency of 7.5 Hz, whereas the ADVP measures 3D velocity vectors in a...

Saturation of curvature-induced secondary flow, energy losses, and turbulence in sharp open-channel bends: Laboratory experiments, analysis, and modeling

The paper investigates the influence of relative bend curvature on secondary flow, energy losses, and turbulence in sharp open-channel bends. These processes are important in natural streams with respect to sediment transport, the bathymetry and planimetry, mixing and spreading of pollutants, heat, oxygen, nutrients and biological species, and...

Large-eddy simulation of a curved open-channel flow over topography

Large-eddy simulation (LES) is performed of a curved open-channel flow over topography based on the laboratory experiment by Blanckaert [“Topographic steering, flow circulation, velocity redistribution and bed topography in sharp meander bends,” Water Resour. Res., doi:10.1029/2009WR008303 (in press)] . In the experiment, the large-scale bed...

Meander dynamics: A nonlinear model without curvature restrictions for flow in open?channel bends

Despite the rapid evolution of computational power, simulation of meander dynamics by means of reduced and computationally less expensive models remains practically relevant for investigation of large?scale and long?term processes, probabilistic predictions, or rapid assessments. Existing meander models are invariantly based on the assumptions...

Hydrodynamic processes in sharp meander bends and their morphological implications

The migration rate of sharp meander bends exhibits large variance and indicates that some sharply curved bends tend to stabilize. These observations remain unexplained. This paper examines three hydrodynamic processes in sharp bends with fixed banks and discusses their morphological implications: secondary flow saturation, outer-banks cells, and...

A parameter study on bank shear stresses in curved open channel flow by means of large-eddy simulation

Meandering rivers and streams are a common planform in the world’s populated areas. Furthermore the recent increased focus on renaturalization projects has lead policy makers to also consider the partial remeandering of previously trained rivers. Economic factors such as navigation, man-made infrastructure and valuable farm land set the boundary...

Nonlinear simulation of meander evolution

Evolution of meanders, a complex morpho-dynamic process, has been the focus of research challenging river engineers for decades. The study replicates the natural evolution of meandering processes by coupling the Bank Erosion and Retreat Model (BERM, by Chen and Duan) with a nonlinear flow model (by Blanckaert and de Vriend). Distinguished from...

Toward nonlinear modeling of meander evolution

Meander dynamics: A reduced-order nonlinear model without curvature restrictions for flow and bed morphology

Reduced-order models remain essential tools for meander modeling, especially for processes at large length scales and long time scales, probabilistic simulations, rapid assessments, or when input data are scarce or uncertain. Present reduced-order meander models consider their dependent variables either as small-amplitude variations compared to...

Exergaming improves balance in children with spastic cerebral palsy with low balance performance: results from a multicenter controlled trial

Purpose: Previous studies investigating the effectiveness of exergame balance-training (using video-games) in children with cerebral palsy (CP) yielded inconsistent results that could be related to underpowered studies. Therefore, in this multicenter intervention study, we investigated whether exergaming improves balance clinically in spastic...