Authors: Takaaki Okamoto Iehisa Nezu
Publish Date: 2013/03/03
Volume: 13, Issue: 5, Pages: 417-434
Abstract
A number of experimental studies on submerged canopy flows have focused on fullydeveloped flow and turbulent characteristics In many natural rivers however aquatic vegetation occurs in patches of finite length In such vegetated flows the shear layer is not formed at the upstream edge of the vegetation patch and coherent motions develop downstream Therefore more work is neededz to reveal the development process for largescale coherent structures within vegetation patches For this work we considered the effect of a limited length vegetation patch Turbulence measurements were intensively conducted in openchannel flows with submerged vegetation using Particle Image Velocimetry PIV To examine the transition from boundarylayer flow upstream of the vegetation patch to a mixinglayertype flow within the patch velocity profiles were measured at 33 positions in a longitudinal direction A phenomenological model for the development process in the vegetation flow was developed The model decomposed the entire flow region into four zones The four zones are the following i the smooth bed zone ii the diverging flow zone iii the developing zone and iv the fullydeveloped zone The PIV data also confirmed the efficiency of the mixinglayer analogy and provided insight into the spatial evolution of coherent motions
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