Flow characteristics of rectangular open channels with compound vegetation roughness

doi:10.1007/s10483-016-2035-6

Applied Mathematics and Mechanics (English Edition) ›› 2016, Vol. 37 ›› Issue (3): 341-348.doi: https://doi.org/10.1007/s10483-016-2035-6

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Flow characteristics of rectangular open channels with compound vegetation roughness

Yuhong ZENG, Wenxin HUAI, Mingdeng ZHAO

State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China

Received:2015-03-12 Revised:2015-08-13 Online:2016-03-01 Published:2016-03-01
Contact: Yuhong ZENG E-mail:yhzeng@whu.edu.cn
Supported by:
Project supported by the National Natural Science Foundation of China (Nos. 51379154, 51479145, and 51439007) and the Program for New Century Excellent Talents in University of China (No.NCET-11-0393)

Abstract

Abstract:

An idealized parallel flow caused by a lateral bed roughness difference due to the partial vegetation across a channel is investigated. Similar to the flow in a compound channel, there are mixing layers adjacent to the interface between the vegetation and the non-vegetation lanes, and a lateral momentum exchange occurs between the slow-moving water in the former lane and the fast-moving water in the latter lane. Under a uniform flow condition, the three-dimensional (3D) instantaneous velocities of two cases with different discharges and water depths are measured with a 16MHz acoustic Doppler velocimeter (micro ADV). The longitudinal variation of the streamwise velocity and the vertical variation of the Reynolds stress are analyzed. A quadrant analysis is carried out to investigate the outward and inward interaction, ejection, and sweep phenomenon caused by the vegetation variation across the channel. The results show that the flow characteristics in the vegetation lane are similar to those in an open channel fully covered with submerged vegetation, and the flow characteristics in the smooth non-vegetation lane are similar to those in a free open channel. For the cases studied here, the width of the mixing region is about 10% of the channel width, and the mixing region is mainly on the non-vegetation half.

Key words: vegetated flow, lateral momentum exchange, acoustic Doppler velocimeter (ADV), quadrant analysis, mixing layer

2010 MSC Number:

76F25

Yuhong ZENG, Wenxin HUAI, Mingdeng ZHAO. Flow characteristics of rectangular open channels with compound vegetation roughness. Applied Mathematics and Mechanics (English Edition), 2016, 37(3): 341-348.

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Flow characteristics of rectangular open channels with compound vegetation roughness

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