下荆江急弯段河床形态调整对水流特性的影响  

Influence of riverbed geomorphic adjustment on flow characteristics in a sharp bend of the Lower Jingjiang Reach

作　　者：刘胜琪 夏军强[1] 邓珊珊[1] 李志威 LIU Sheng-qi;XIA Jun-qiang;DENG Shan-shan;LI Zhi-wei(State Key Laboratory of Water Resources and Hydropower Engineering Science,Wuhan University,Wuhan 430072,China)

机构地区：[1]武汉大学、水资源与水电工程科学国家重点实验室,湖北武汉430072

出　　处：《泥沙研究》2023年第2期9-16,共8页Journal of Sediment Research

基　　金：国家自然科学基金项目(51725902,U2040215);湖北省自然科学基金创新群体项目(2021CFA029);湖北省自然科学基金面上项目(2020CFB554)。

摘　　要：三峡水库运用后下荆江急弯段出现“凸冲凹淤”现象,研究急弯段河床形态调整对水流特性的影响十分必要。基于2002年、2011年和2016年实测地形,采用Delft 3D水动力学模型计算上游来流为5 000 m^(3)/s、10 000 m^(3)/s和20 000 m^(3)/s流量的七弓岭急弯段水流特性,探讨河床形态调整对弯道段流速分布与二次流结构和强度的影响。结果显示:七弓岭急弯段2002年至2016年的水流动力轴线大幅左摆,三种流量级条件下分别左摆1 160 m、1 130 m和900 m;水流冲刷动力在凸岸增强,凹岸减弱。这三年的凸岸侧垂线平均流速最大值依次为1.24 m/s、1.91 m/s和1.66 m/s。凹岸侧最大流速依次为2.55 m/s、0.97 m/s和0.80 m/s。七弓岭弯顶上游的断面平均环流强度递减,凹岸沙洲的二次流已非常微弱,导致泥沙淤积。Processes of chute cutoff occurred in sharp bends of the Lower Jingjiang Reach with the formation of sand bars near the concave bank zone after operation of the Three Gorges Project.Based on the observed topographic data of the Qigongling Reach in 2002,2011 and 2016,flow characteristics are simulated with the discharges of 5 000 m^(3)/s,10 000 m^(3)/s and 20 000m^(3)/s by Delft 3D hydrodynamic model.Influences of riverbed geomorphic adjustment on velocity distribution,secondary flow structure and intensity are discussed.Results show that the flow dynamic axis in Qigongling bend swung left significantly from 2002 to 2016.Under the condition of the three discharges,it swung 1 160 m,1 130 m and 900 m respectively.Flow scouring intensity increased in convex bank zone while decreased in concave bank zone.The maximum depth-averaged velocity in the three years were 1.24 m/s,1.91 m/s and 1.66 m/s sequentially in convex bank zone.The maximum of depth-averaged velocity were 2.55 m/s,0.97 m/s and 0.80 m/s sequentially in concave bank zone.The average circulation intensity of a section at one quarter of Qigongling bend showed a decreasing trend.There was almost no flow circulation at the concave bank sandbar,which induced conducive conditions for sediment deposition.

关 键 词：急弯河段 凸岸崩退 沙洲发育 二次流 水动力学模型 

分 类 号：TV147.3[水利工程—水力学及河流动力学]