水浮莲型生态河道水流纵向流速垂线分布规律  

Vertical profiles of longitudinal velocity in ecological channel flow with water lettuce

作　　者：王洁琼[1] 槐文信[1] 李志伟[1] 

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：《武汉大学学报（工学版）》2011年第4期439-444,共6页Engineering Journal of Wuhan University

基　　金：教育部博士点基金项目(编号:20100141110028);武汉市学科带头人资助计划;中央高校基本科研业务费专项资金项目(编号:2104001)

摘　　要：通过物理模型试验、理论分析和数值模拟的方法,研究了有水浮莲覆盖水流的纵向流速垂线分布规律.在水浮莲全覆盖条件下,初步对比分析了3种不同工况下水流纵向时均流速的变化趋势和垂线分布特点.通过"双层边壁"假设,以最大流速线(点)为界将流动沿水深方向分成两层等效明渠流流动层:植被下层和床面上层,并假定上下两层互不影响,即分别只受植被底部和床面粗糙程度影响;利用混合长度模型简化时均动量方程,推导出有水浮莲覆盖水流在恒定均匀流下的纵向时均流速对数分布公式;根据实测数据对公式进行了验证分析.水浮莲对水流影响的数值模拟主要利用计算流体力学软件FLUENT,结合可实现双方程紊流模型,对有水浮莲覆盖的水槽二维两相流场作了数值模拟,并采用多孔介质域模拟水浮莲覆盖区域,将数值计算得到的流速分布与试验实测结果进行了比对,两者吻合较好.The determination of vertical profiles of stream wise velocities in a vegetated channel is a difficult task due to the complex effects of the vegetation cover that involve anisotropic turbulence.To study the vertical velocity distribution in flows through water lettuce,this paper adopts physical experiments,theoretical analysis and numerical simulation methods.According to the physical model experiments,three groups of data about stream wise velocities are obtained.An initial analysis of the characteristics of longitudinal velocity distribution in a full-vegetated channel has been given.The proposed hypothesis of ＂double-layer wall＂ means the flow can be divided into two layers that consist of near-bed area and vegetation-below area by the maximum flow velocity line（point） and one flow layer is equal to an open channel without influencing on the other one.A mixing-length model for predicting vertical velocity distribution in flows through emergent vegetation is used to simplify the mean momentum equation,which yields the formulas of logarithmic distribution of longitudinal velocity of steady uniform flow in the open channel covered with water lettuce.A wide range of longitudinal velocity profile data for open channels has been used for validating the formulas.The agreement between the measured and the computed velocities is rather good,despite the simplification is used.The FLUENT combined with the realizable k-ε model offers the result of numerical simulation in the 2D two-phase flow.Porous medium conditions of turbulence also promote the agreement between the measured and the calculated velocities.

关 键 词：水浮莲 纵向流速 双层边壁 可实现k-ε模型 多孔介质域 

分 类 号：TV133.1[水利工程—水力学及河流动力学]