摘要
针对健康生态环境下的河道系统性向外分汊演化、河道-植物和谐发展现象,以实际河型资料特征统计为基础,设计了外分单汊的常曲率弯道水流特征数模试验,研究了主弯道不同弯曲比率和汊道出口不同开闭条件的影响.汊道的存在对主河道下游蜿蜒迁移趋势具有强化效应,且此效应以临界弯曲条件(曲率半径/河宽=3.0)为中心向更强弯和更缓弯发展趋势双向扩散.汊道的存在引起弯道下游横断面凹岸侧近底部“强-正涡量区”与凸岸侧近水面“弱-负涡量区”的此消彼长,两者最终相互中和、抵消.汊道出口的自由出流引起弯道下游横断面和整体近床水平面螺旋流强度的大幅减小和强弯条件下弯段上游横断面螺旋流强度的明显增大.壁面切应力在分叉口头部趋小,在局部汇流区趋大,且在汊道出口自由出流时二者均大幅增大,分叉口对应的主河道凸岸侧下游壁面和弯道最下游1/4段床面切应力均降至极低.该研究为河道系统中植物发展的和谐物理空间设计提供了基础性水信息支持.
This study aimed at the systematically outward branching phenomenon in river channels and the harmonious development between channels and plants under the healthy ecological environments,designed the numerical modelling tests on flow characteristics in a constant curved bend with outward single short-branch based on field river statistics,and investigated the various influences of main-channel curvature ratio and branch outlet on-off condition.The presence of branch had strengthening effects on the downstream main-channel migration potential,and such effects spread towards both the stronger and weaker bending tendencies around the critical bending state(ratio of curvature radius to channel width equals to 3.0).The presence of branch caused the wane and wax of"the strong and positive vortex zone"near the bed around the outer-bank side and"the weak and negative vortex zone"near the surface around the inner-bank side in the downstream channel,and the final neutralization of the these two.The outflow state of branch led to the significant decreases of helical flow strength at both the cross-sections along the downstream channel and horizontal sections near the overall channel bed,and the significant increases of helical flow strength at the cross-sections along the upstream channel under the strong bending conditions.The shear stresses tended to decrease at the bifurcation head and become larger around the local confluence zone,particularly,when freeing the branch flow,both of them would significantly increase,and the shear stresses at both the downstream inner sidewall and the most downstream quarter of bend bed would drop to the extremely low value states.This study provided the fundamental hydro-informatic supports to harmoniously physical space design for plants development in river system.
作者
宋晓龙
陈有俊
黄海
徐海珏
白玉川
SONG Xiaolong;CHEN Youjun;HUANG Hai;XU Haijue;BAI Yuchuan(State Key Laboratory of Hydraulic Engineering Intelligent Construction and Operation,Tianjin University,Tianjin 300350,China;Institute for Sedimentation on River and Coastal Engineering,Tianjin University,Tianjin 300350,China;Key Laboratory of Hydro-Sediment Science and River Training,the Ministry of Water Resources,China Institute of Water Resources and Hydropower Research,Beijing 100038,China)
出处
《应用基础与工程科学学报》
EI
CSCD
北大核心
2023年第5期1095-1109,共15页
Journal of Basic Science and Engineering
基金
中国水利水电科学研究院水利部水沙科学与江河治理重点实验室开放研究基金项目(IWHR-JH-2020-A-02)
国家自然科学基金项目(52009145)
天津市科技计划项目(21JCQNJC00480)。
关键词
外分单汊
健康生态环境
常曲率弯道
水流特征
弯曲比率
汊道出口条件
螺旋流
切应力
outward single branch
healthy ecological environment
constant curved bend
flow characteristics
curvature ratio
branch outlet condition
helical flow
shear stress
