Predictive Method for the Evolution of Flow Velocity in an Open Channel with a Floating Vegetation
Floating canopies are often distributed in open channels,altering the flow velocity evolution and affecting the nutrient removal effi-ciency of floating vegetation.The flow in an open channel with a floating vegetation canopy is vertically divided into the vegetated region and the bare channel.As the flow enters a floating canopy,the flow along the canopy's leading edge adjusts,and the in-canopy velocity continuously di-minishes over the interior adjustment distance,XD,due to vegetation drag.Beyond XD(x>XD),the flow becomes fully developed,and the velo-city remains constant.Inside a floating canopy,the interior adjustment distance,XD,is defined as the distance from the canopy's leading edge to the position where the flow is fully developed.A model based on exponential decay and the flow continuity equation is proposed to predict the longitudinal profiles of streamwise velocities within and below a floating canopy.The proposed model does not include a calibration parameter,and all input parameters can be obtained from flow and vegetation conditions,which is advantageous for its application.Twelve groups of experi-mental data from various sources are utilized to verify the proposed model.The model accurately predicts the velocity evolution within and below the floating canopy of vegetation.This study proposes a predictive model for the longitudinal profiles of streamwise velocities in an open channel with a floating canopy,providing a theoretical basis for river ecological restoration and water resource management.
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