Flow characteristics in open channels with aquatic rigid vegetation

Different types of vegetation widely exist in rivers and wetlands. The vegetation will affect the ecological environment and flow process, thus becoming increasingly significant in river engineering and aquatic environmental management. Previous research on vegetated flow is mainly to understand the flow structure of open channels with fully covered one-layer vegetation. However, vegetation often grows along a river bank and co-exists in different heights. The present paper presents experimental results about the flow characteristics of an open-channel with two sides covered by differently layered vegetation, focusing on the effect of vegetation on the velocity distribution and discharge. Two heights of dowels in 10 cm and 20 cm were used to simulate rigid vegetation and arranged in a linear form on both sides of a channel bed under emergent and fully submerged flow conditions. The velocity at different positions was obtained using ADV (Acoustic Doppler Velocimetry). Measured results demonstrate that there exists a shear layer between free-flow and vegetated zones, indicating that the flow transition occurs between fast-moving flow in the free zone and slowly obstructed flow in the vegetated zone and induces a high shear layer and transverse coherent vortices near the interface. Furthermore, compared with the emergent condition, the discharge through the free-flow region slightly decreases under full submerged conditions while the discharge in the vegetated region increases, indicating that the vegetation does not significantly change the discharge percentage in the free region. These findings on differently-layered vegetation would help riparian management practices to maintain healthy ecological and habitat zones.

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Flow characteristics of rectangular open channels with compound vegetation roughness

Applied Mathematics and Mechanics ◽

10.1007/s10483-016-2035-6 ◽

2016 ◽

Vol 37 (3) ◽

pp. 341-348 ◽

Cited By ~ 4

Author(s):

Yuhong Zeng ◽

Wenxin Huai ◽

Mingdeng Zhao

Keyword(s):

Flow Characteristics ◽

Open Channels

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A method for the formulation of Reynolds number functions

Canadian Journal of Civil Engineering ◽

10.1139/l00-002 ◽

2000 ◽

Vol 27 (4) ◽

pp. 829-833 ◽

Cited By ~ 3

Author(s):

Ana Maria AF da Silva ◽

Tirupati Bolisetti

Keyword(s):

Reynolds Number ◽

Sediment Transport ◽

Flow Characteristics ◽

Mathematical Expression ◽

Open Channels ◽

Strong Variation ◽

Mathematical Expressions ◽

Flow And Sediment Transport ◽

Shields Curve ◽

General Method

A general method for the formulation of flow characteristics which are functions of the Reynolds number of the system is presented. It is assumed that the flow characteristics exhibit a strong variation with the Reynolds number when the Reynolds number is "small," and that they become independent of it when the Reynolds number is "large." The method is illustrated by finding mathematical expressions for the experimentally determined "roughness" function curve and for the sediment transport initiation curve (Shields' curve), which are relevant for the analysis of flow and sediment transport in pipes and open channels. The two expressions thus obtained can be used in practice for computational purposes.Key words: Reynolds number functions, mathematical expression, roughness function, Shields' curve.

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