A circular cylinder in the main-channel/floodplain interface of a compound channel: effect of the shear flow on drag and lift

The interface between the main channel and the floodplain of a compound channel is often populated by trees or buildings that normally remain emergent during floods. This study investigates how drag on an emergent cylinder is affected by the shear flow that develops at the interface. The experimenta...

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Bibliographic Details
Published in:Journal of hydraulic research 2020-04, Vol.58 (3), p.420-433
Main Authors: Gymnopoulos, Miltiadis, Ricardo, Ana M., Alves, Elsa, Ferreira, Rui M.L.
Format: Article
Language:English
Subjects:
Circular cylinders
Compound channel
Compound channels
Conservation of momentum
cylinder drag
Cylinders
Drag
Drag coefficient
Drag coefficients
Drag reduction
Floodplains
Momentum
open channel flow turbulence
Reynolds-averaged integral momentum equations
Shear flow
Shear layers
turbulent wakes
Uniform flow
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Summary:The interface between the main channel and the floodplain of a compound channel is often populated by trees or buildings that normally remain emergent during floods. This study investigates how drag on an emergent cylinder is affected by the shear flow that develops at the interface. The experimental set-up features a circular cylinder at the interface of a straight compound channel under uniform flow conditions. The integral form of the equation of conservation of momentum was used to calculate the magnitude and direction of the time-averaged drag force per unit submerged-length of the cylinder. All terms were experimentally determined, except for those associated with fluid interaction with the cylinder. The same method was also applied to a cylinder under symmetrical flow conditions. It is concluded that the existence of the shear layer leads to an asymmetrical drag force and to a reduced drag coefficient.
ISSN:0022-1686
1814-2079
DOI:10.1080/00221686.2019.1596987