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An experimental study on main flow, secondary flow and turbulence in open-channel bends with emphasis on their interaction with the outerbank geometry

English title An experimental study on main flow, secondary flow and turbulence in open-channel bends with emphasis on their interaction with the outerbank geometry
Applicant Schleiss Anton
Number 119835
Funding scheme Project funding (Div. I-III)
Research institution Plateforme de constructions hydrauliques EPFL ENAC IIC PL-LCH
Institution of higher education EPF Lausanne - EPFL
Main discipline Civil Engineering
Start/End 01.04.2008 - 31.10.2008
Approved amount 31'137.00
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Keywords (12)

open-channel bend; river meander; secondary flow; turbulence; bank inclination; MIXING COEFFICIENT; curbed flow; bank erosion; bank shear stress; roughness; curvature; meander

Lay Summary (English)

Lead
Lay summary
In the framework of river restoration, a tendency to reverse previous river canalization works: straight channels are transferred into smoothly meandering channels in order to give them some controlled freedom in their alluvial plane, which is recognized as a rich biotope and as an important factor in flood defense systems by providing buffer capacity. The so-called “third correction of the Rhone river” is an example of an important river training and rehabilitation project in Switzerland: it is a 30- years project with an estimated cost of about 1 billion SF.

The confinement of the river by protecting its bank against erosion is a major component of such river projects. Outer banks in bends are most vulnerable to erosion, which can lead to bank failure, subsequent devastating inundations and river displacement. To date, no reliable engineering tools are available for the design of river rehabilitation projects and environmentally integrated bank protection schemes, which is due to the insufficient understanding of the relevant physical processes. Secondary circulation, near-bank patterns of mean flow and turbulence, curved flow turbulence and bank erosion are known to be such poorly understood processes.

The projects investigates systematically in a laboratory flume the influence of the roughness and the inclination of the outer bank in open-channel bends on the patterns of main flow, secondary flow, turbulence, as well as on the boundary shear stress and the mixing characteristics.

The availability of such accurate experimental data concerning 3D flow and turbulence is a requisite to enhance our understanding and to improve our river management and engineering tools, since the overwhelming majority of available experimental data is at present limited to straight uniform flow.

Experimental data obtained in this project generate new insight in the physics of curved open-channel flow and its modeling, and lead to the development of more reliable tools for river management and engineering. They are essential for the validation of numerical codes developed in the framework of the complementary projects.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

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Associated projects

Number Title Start Funding scheme
125095 Influencing river morphodynamics by means of bubble screens. Fundamentals and application to open-channel bends. 01.10.2009 Project funding (Div. I-III)
103932 An experimental study on main flow, secondary flow and turbulence in open-channel bends with emphasis on their interaction with the outerbank geometry 01.08.2004 Project funding (Div. I-III)

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