Investigating the Effect of Relative Width on Momentum Transfer between Main Channel and Floodplain in Rough Rectangular Compound Channel Sunder Varius Relative Depth Condition

Shima Bahadori,Mehdi Behdarvandi Askar

doi:10.4236/ojg.2016.64020

Abstract

Compound section is referred to a section the surface of which is made of several sub-sections with different flow characteristics. The difference in the hydraulic and geometry characteristics causes a complexity in flow hydraulic and creates an interaction between the main channel and floodplains, resulting in an apparent shear stress and a transverse momentum transfer. The amount of such a stress plays an important role in many river engineering measures [1]. Due to the flow complexity, the common approximate analytical methods are not enough to identify the flow profile. The FLOW3D Software with its great features in three-dimensional analysis of flow field is used as a tool to investigate the shear stress in a direct symmetrical compound rectangular channel. After the simulation of models, it is found that an increase in the relative width and relative depth parameters decreases the percentage of apparent shear stress and an increase in the relative roughness causes it to be increased [2].

Highlights

Compound section is referred to a section the surface of which is made of several sub-sections with different flow characteristics
Since no study had directly investigated the effect of some parameters as well as the apparent shear stress with the FLOW3D software, this study aims to investigate the effects of relative depth, the relative width, and relative roughness on the transfer of momentum and apparent shear stress in a rectangular, straight, and symmetric compound channel with the use of the FLOW3D software [10]
In order to evaluate the effect of relative roughness parameters and the relative width on the apparent shearing stress, the following charts are drawn

Summary

Introduction

Compound section is referred to a section the surface of which is made of several sub-sections with different flow characteristics. In the absence of a flood, the flow only transits from the main waterway and floodplains generally remain without any flow, resulting in a lesser degree of roughness of the main channel compared to the floodplains This difference in roughness during floods and flowing of stream from flood plains leads to a difference between the velocities in the sub sections. The difference in values of the aforementioned parameters is followed by the complexity of the hydraulic flow Such differences cause an interaction between deep flow in the main channel and shallow flow in the floodplains the result of which is a shear stress which is in addition to the bed and walls shear stress and is generally called apparent shear stress. This apparent shear stress dramatically violates flow pattern and boundary shear stress [3]

Objectives

Methods

Findings

Conclusion