摘要
窝崩是长江中下游常见的一种崩岸类型,具有流场结构复杂、发展速度快、破坏力强等特点。为揭示不同类型窝崩三维水流结构的特点,以长江中游虾子沟和下游扬中窝崩为例,设计了一般型与口袋型的窝崩概化模型,开展了相应的水槽试验。采用PIV流场测量技术,获得了一般型和口袋型窝崩的三维流场,研究了这2类窝崩的水流结构。试验结果表明:(1)窝塘及附近区域可分为主流区、掺混区和回流区;(2)一般型与口袋型窝崩回流区流速的最大值分别为主流平均流速的0.19倍和0.27倍,掺混区存在着较大的流速梯度且紊动强度大,掺混宽度沿主流方向逐渐增大;(3)一般型窝崩回流区的垂向平均流速比口袋型大48%~76%,且回流中心相比于口袋型更靠近窝塘外侧,这导致一般型窝崩更易将窝塘内泥沙输运至主流区;(4)在较高主流流速条件下,一般型窝崩窝塘水体与主流的交换速率大于口袋型窝崩,较低主流流速下则相反。
Arc-shaped bank erosion is a common type of bank erosion in the middle and lower reaches of the Yangtze River.It has the characteristics of complex three-dimensional(3-D) flow structures, rapid expansion, and strong destructive capacity.The general and pocket types of arc-shaped bank erosion models were designed on the basis of actual bank erosion events.3-D flow fields in general and pocket-type bank erosion zones were obtained from generalized tests by using particle image velocimetry technology.Flow structure and turbulence characteristics were analyzed.Results showed the following:(1) The arc-shaped bank erosion zone can be divided into the main flow, mixing, and backflow zones in accordance with the flow structures and distributions of turbulent intensity.(2) In the mixing zone, the velocity gradient and turbulence intensity were large, and the width of the mixing zone gradually increased along the main flow direction.The maximum values of the flow velocity at the backflow zone of the general and pocket types were approximately 0.19 and 0.27 times the average velocity of the mainstream, respectively.(3) The vertical average flow velocity at the backflow region of the general bank erosion zone was 48%—76% larger than that in the pocket-type bank erosion zone.The backflow center of the general bank erosion type was closer to the outer side of the bank erosion zone than that of the pocket-type bank erosion zone, thus facilitating the transport of sediment from the bank erosion zone to the main flow area.(4) Under the condition of high mainstream flow velocity, the exchange rate between the water in the general-type bank erosion zone and the main flow was higher than that in the pocket-type bank erosion zone, and the opposite was true under low mainstream flow velocity.
作者
孙启航
夏军强
邓珊珊
周美蓉
司金华
张幸农
SUN Qihang;XIA Junqiang;DENG Shanshan;ZHOU Meirong;SI Jinhua;ZHANG Xingnong(State Key Laboratory of Water Resources and Hydropower Engineering Science,Wuhan University,Wuhan 430072,China;State Key Laboratory of Hydraulics and Mountain River Engineering,Sichuan University,Chengdu 610065,China;State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering,Nanjing Hydraulic Research Institute,Nanjing 210029,China)
出处
《水科学进展》
EI
CAS
CSCD
北大核心
2023年第1期144-156,共13页
Advances in Water Science
基金
国家自然科学基金资助项目(51725902
U2040215)。
关键词
窝崩
三维流场
紊动强度
粒子图像测速技术
水槽试验
arc-shaped bank erosion
three-dimensional flow field
turbulence intensity
particle image velocimeter
laboratory experiments
