摘要
连续曲率弯曲河道是河流的常态,而河道弯曲引起的二次流是河床地形和河岸变动的主要动力.采用三维多普勒高级点式流速仪和Trimble TX8三维扫描仪,分别对模型40个断面和床面形态进行三维流速数据和床面形态数据采集.通过水流和床面试验,研究了连续曲率弯道水槽水流结构变化与床面形态短期演变特性.研究结果表明:模型弯道处水面发生扭曲,最大横比降位于各弯段弯顶下游.纵向流速在垂向上呈先增大后减小的趋势,这体现了明渠水流最大流速发生在自由水面以下.各断面存在一个主环流和一个反向小环流,部分断面出现3个或更多环流结构,且环流出现的位置横向流速在垂向上改变方向.环流强度最小值位于各弯段弯顶附近.在各弯段凹岸附近,纵向流速存在小流速区,床面形态均存在与小流速区相对应的床面平整区.活体柔性植被均匀种植的工况Run-4最大淤积和冲刷深度均小于无植被种植的工况Run-3,这说明弯曲边界引发的二次环流是河床地形的主要动力.活体柔性植被根系和植株对床沙和水流均产生影响,起到了增大河床阻力的作用.
The basic form of rivers is the continuous curved channel,and the secondary circulation caused by the curvature of this channel is the main driving force of changes in the bed topography and bank line.In this study,we used acoustic Doppler velocimetry(ADV)and a Trimble TX83D scanner to collect 3D flow velocity data from 40 model sections and river bed topography.We then experimentally investigated the change in the flow structure of a flume with continuous curvature and its morphological short-term evolution.The results show that the water surface profile is distorted at the curve of the channel,and the maximum transverse gradient occurs at the downstream apex of each bend.The longitudinal velocity was generally found to first increase and then decrease in the vertical direction,which indicates that the maximum velocity of the open channel flow occurs below the free water surface.One main circulation and a reverse small circulation occurred in each section,with three or more circulation structures appearing in some sections,where the transverse circulation velocity changes direction vertically.The minimum circulation intensity occurs near the top of each bend.Near the concave bank in each curved section,there is a small longitudinal velocity zone where the bed morphology exhibits a small flat area.Moreover,the maximum deposition and scour depth of Run-4,which is covered with an even layer of living vegetation,are less than those of Run-3,which has no vegetation coverage.This indicates that the secondary circulation induced by the curved boundary is the main force driving the bed topography,and the roots and plants comprising the living flexible vegetation affect the bed sand and water flow and increase the bed resistance.
作者
曹玉芬
白玉川
高术仙
Cao Yufen;Bai Yuchuan;Gao Shuxian(State Key Laboratory of Hydraulic Engineering Simulation and Safety,Tianjin University,Tianjin 300072,China;Tianjin Research Institute for Water Transport Engineering,Ministry of Transport,Tianjin 300456,China)
出处
《天津大学学报（自然科学与工程技术版）》
EI
CSCD
北大核心
2020年第12期1226-1235,共10页
Journal of Tianjin University：Science and Technology
基金
国家重点基础研究发展计划资助项目(2018YFF0212202)
国家自然科学基金青年基金资助项目(51809130)
中央级公益性科研院所基本科研业务费专项资金资助项目(TKS180104).
关键词
正弦派生弯道水槽
二次环流
活体柔性植物
床面形态
sine-generated meandering channel
secondary circulation
living flexible vegetation
bed topography
