Tributary Channel Width Effect on the Flow Behavior in Trapezoidal and Rectangular Channel Confluences

Aliasghar Azma,Yongxiang Zhang

doi:10.3390/pr8111344

Abstract

Channel confluences happen commonly in water transport networks and natural rivers. Utilizing a 3D CFD code, a series of numerical simulations were performed using a large eddy simulation turbulence model to investigate the effect of the variations in tributary channel width and the transverse geometrical shape of the main channel on the flow parameters and vertical structure in a T-shape confluence. The code was calibrated using the experimental data from the literature. Flow parameters were considered in ratios of tributary width to the main channel width in trapezoidal and rectangular channels. Results indicate that decreasing the width ratio of the tributary channel to the main channel significantly affects the flow structure in the confluence. Generally, it increases the width and length of the main recirculation zone. It also increases the maximum velocity near the bed, especially in cases with a trapezoidal shape. Besides, it highly affects the structure and formation of the recirculation zone in trapezoidal channels.

Highlights

Confluences are important structures due to the highly turbulent and complex flow structure forms at the junction section
In natural and man-made channels, especially in simple channels such as drainage canals, the separation zone is a dominant component of the flow structure due to the sharp-edged form of the canals and their bed-level concordance [11,12]
Results show that increasing the W* from 0.25 to 1 highly to to

Summary

Introduction

Confluences are important structures due to the highly turbulent and complex flow structure forms at the junction section. Different geometrical and hydraulic parameters including planform, cross-sectional shape, bed-level concordance or discordance, the momentum flux ratio [1,2,3,4,5] and the density difference between streams [6] affect the hydraulic and fluvial processes within and around the channel confluences. Researchers, including Taylor [10], Webber and Greated [11], Shumate [12], and Mignot et al [13], have emphasized the discharge ratio of side-channel to the main channel (momentum flux ratio) as the key parameter controlling the flow structure. In natural and man-made channels, especially in simple channels such as drainage canals, the separation zone is a dominant component of the flow structure due to the sharp-edged form of the canals and their bed-level concordance [11,12].

Methods

Results

Conclusion