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標題: Observations on flow and local scour around submerged flexible vegetation
作者: Chen, Su-Chin
Chan, Hsun-Chuan
Li, Yu-Hsiu
關鍵字: Vegetation;Velocity measurements;Scour
Project: Advances in Water Resources, Volume 43, page(s) 28–37.
This study experimentally investigated the effects of submerged vegetation on the characteristics of flow
and the formation of a scour hole. The submerged vegetations were modeled by bundled plastic fibers.
Experiments were performed for various spacings of the plastic fibers, resulting in vegetation density
ranging from 0.21 to 0.65. The vegetation models were aligned with the approaching flow in a rectangular
channel. Vertical distributions of time-averaged velocity and turbulence intensity at various streamwise
distances were evaluated using an acoustic Doppler velocimeter (ADV). The characteristic lengths of the
scour hole, including scour depth, dune height, the length of the scour hole, the horizontal distance of the
maximal scour depth, and the horizontal distance of the dune crest, were determined from the bed profiles.
Velocity and turbulence intensity plots indicated that the deflected flow over the vegetation was
promoted with the decrease in spanwise spacing. Downstream of the vegetation zone, two shear layers
developed from the vegetation zone. As the spanwise plant spacing increased, the turbulence intensity of
the upper shear layer decreased because of the strong flow through the vegetation. Vegetation densities
were used to examine the effects of vegetation on the characteristic lengths of the scour hole. Scour
depth, dune height, length of the scour hole, horizontal distance of the maximal scour depth, and horizontal
distance of the dune crest increased linearly with a decrease in vegetation density.
ISSN: 0309-1708
DOI: 10.1016/j.advwatres.2012.03.017
Appears in Collections:水土保持學系

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