An Analytical Model for the Distributions of Velocity and Discharge in Compound Channels with Submerged Vegetation.

Beihan Jiang,Kejun Yang,Shuyou Cao,Vanesa Magar

doi:10.1371/journal.pone.0130841

Abstract

Based on the momentum transfer theory, an analytical model is proposed for the velocity and discharge distributions in compound channels with submerged vegetation on the floodplain. The partially vegetated channel was divided into three sub-regions, i.e. the main channel region, the floodplain region with submerged vegetation and the floodplain region without vegetation. For each region, the force balance relationship was established, and the momentum transfer between different regions was presented. Verification by the experimental data and comparison with the traditional method shows that the proposed method is capable of predicting for the velocity and discharge distributions in compound channels with submerged vegetation and is superior to the conventional method. The results also show that when the momentum transfer between different regions is ignored, the computed discharge will be much lager than the measured data, and the error increases with the discharge, especially in the floodplain region.

Highlights

A compound channel consisting of a main channel and one or two floodplains yields complex flow conditions
Substituting Eqs (11–13) into Eqs (9) and (10) gives, ta where α is defined as the momentum transfer coefficient, and V1 and V2 are the mean velocities in the main channel and the floodplain region with vegetation
An analytical model is proposed for the velocity and discharge distributions in compound channels with submerged vegetation on the floodplain,based on momentum theory

Summary

Introduction

A compound channel consisting of a main channel and one or two floodplains yields complex flow conditions. Huai et al [29,30], Tang and Knight [31, 32], Liu et al [33] established the governing equations of flow in compound channels with vegetated floodplains and gave good predictions for the lateral distributions of depth-averaged velocity and boundary shear stress for the type of channels. In this study, based on the momentum transfer theory [34], an attempt is made to propose a relatively simple, useful mathematical model for the predictions of average flow velocities and discharges for each channel region.

Results

Conclusion