明渠紊流中淹没柔性植被流固耦合大涡数值模拟  

Large Eddy Simulation of Submerged Flexible Vegetation Fluid-Solid Coupling in Open Channel Turbulent Flow

作　　者：许栋[1] 梁心雅 张炳昌 及春宁[1] Xu Dong;Liang Xinya;Zhang Bingchang;Ji Chunning(State Key Laboratory of Hydraulic Engineering Simulation and Safety,Tianjin University,Tianjin 300072,China)

机构地区：[1]天津大学水利工程仿真与安全国家重点实验室,天津300072

出　　处：《天津大学学报（自然科学与工程技术版）》2022年第3期313-321,共9页Journal of Tianjin University：Science and Technology

基　　金：国家重点研发计划重点专项资助项目(2018YFC0407505);国家自然科学基金资助项目(5217090155,51979186,51779175).

摘　　要：水生植被广泛存在于天然河道、湖泊及湿地,是河流生态系统的重要成分.它通过改变明渠水流时均及紊动结构来改变河道水流阻力,并在水流作用下发生弯曲和摆动,形成复杂的流固耦合作用.研究柔性植被在水流作用下的运动响应,能够更精确地解析植被的阻水效应.本文采用基于嵌入式迭代浸入边界法的高效能三维紊流计算程序CgLes,开展流固耦合数值模拟,研究柔性植被在水流作用下的弯曲及运动响应,分析植被涡激振动特性及水流阻力规律.模拟结果表明,植被运动以展向摆动为主导,植被刚度对植被运动轨迹和摆动周期有显著影响,进而影响植被的阻水规律.在水动力条件相同的情况下,植被的摆动周期与植被的弹性模量有关,且不受流场影响.随着刚度系数增大,植被运动模式从准周期性摆动变成周期性摆动,最终发展为刚性情况下的静止直立状态;植被刚度较大且间距较小时,植被存在逆流向弯折现象;在刚度较大时,柔性植被随着水流而摆动,抑制流速发展;但是当柔性植被刚度较小时,植被接近倒伏,明渠的平均流速对比刚性植被情况增大;本文算例中植被刚度对平均流速的影响最大约为2.47%.植被间距对植被的下弯幅度影响较小,但对展向摆幅作用显著;平均流速随植被间距增大而减小,植被间距主要影响植被层内部的水流流速,本文算例中植被间距对平均流速的影响最大约为8.19%.Aquatic vegetation is widely found in natural rivers,lakes,and wetlands,and is an important component of river ecosystems.It increases the influence of channel flow resistance by changing the time-averaged and turbulent structure of open channel flow,and bending and oscillating under the action of water flow,forming a complex flow-solid coupling effect.Studying the motion response of flexible vegetation under the action of water flow is helpful to analyze the water blocking effect of vegetation more accurately.This paper used the high-performance threedimensional turbulence calculation program CgLes based on the built-in iterative immersed boundary method to simulate the flow-solid coupling large eddy,studied the bending and motion response of flexible vegetation under the action of water flow,analyzed the characteristics of vegetation vortex-induced vibration and the law of water flow resistance.The simulation results show that the vegetation movement is dominated by spanwise oscillation.The stiff-ness has a significant impact on the vegetation movement track and swing period,thus affects the water blocking laws of vegetation.Under constant hydrodynamic conditions,the swing period of the vegetation is related to elastic modulus of the vegetation and is not affected by the flow.As the stiffness increases,the vegetation motion changes from quasi-period to period-doubling and finally reaches into the static motion.With the large vegetation stiffness and the small spacing,the reverse-flow bending phenomenon of vegetation may occur.When the stiffness is large,the flexible vegetation swings with the flow,which inhibits the development of flow velocity.However,when the stiff-ness is small enough,the vegetation is close to lodging,and the average velocity of the open channel increases com-pared with it in the rigid vegetation condition.The maximum effect of vegetation stiffness on the average velocity is about 2.47%in this paper.Vegetation spacing has little effect on the bending amplitude of vegetation,but signifi-cant

关 键 词：柔性植被 涡激振动 浸入边界法 流固耦合 数值模拟 

分 类 号：TV133.2[水利工程—水力学及河流动力学]