Effect of a Submerged Vane-Field on the Flow Pattern of a Movable Bed Channel with a 90° Lateral Diversion

Joana Baltazar,António Heleno Cardoso,Elsa Alves,Gökçen Bombar

doi:10.3390/w13060828

Joana Baltazar, António Heleno Cardoso + Show 2 more

Open Access

https://doi.org/10.3390/w13060828

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Abstract

This laboratory study focused on the effect of a submerged vane-field on the flow pattern and bed morphology near and inside the entrance reach of a movable bed 90° lateral diversion. The system was modelled under live bed conditions for a water discharge ratio of ≈0.2. Two experiments were run until bed equilibrium was reached: with and without a vane-field installed close to the diversion entrance to control the transfer of sediments into the diversion channel. The equilibrium bed morphology and the associated 3D flow field were measured in great detail. The bed load diverted into the diversion was reduced by approximately one quarter due to the action of the vane-field. The vanes prevented the formation of the diversion vortex in the main channel, upstream of the diversion’s entrance, thus contributing to that decrease. They also created a main channel vortex that started at the most upstream vanes and further decreased the amount of bed load entering the diversion. The flow separation zone inside the diversion was larger with vanes, but conveyance was balanced through a slightly deeper scour trench therein. The flow structures described were confirmed through the measurements of the turbulent kinetic energy.

Highlights

The area of bed levels below −0.14 m was practically non-existent close to the inner wall of the main channel and it extended towards the diversion entrance, contrary to what happened for the NV case
In the absence of vanes, Barkdoll et al [6] and Herrero et al [8] identified a small number of flow structures in the flow diversion area, considered to cover the flow diversion entrance and the main channel reach influenced by the lateral water extraction
The most important finding of this study was that the vane-field inhibited the development of the diversion vortex, which originated in the main channel in the absence of vanes

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Worked on the first topic, i.e., the morphodynamics of uncontrolled diversions They studied the effects of the angle of diversion, θ, as well as of the channels’ width ratio, Wr , on the depth of the scour trench observed in the main channel. Moghadam et al [16] studied the influence of the discharge ratio, Qr , the vanes’ alignment, β, and the vanes arrangement (parallel or zigzagging) on the transverse Reynolds stresses inside the diversion and near the bed of a θ = 55◦ diversion These authors found that the transverse bed shear stress at the diversion’s entrance was much smaller in the presence of a vane-field than with no vanes in accordance with, for example, Barkdoll et al [6] and others. Sediment transport codes designed to predict the flow field, the bed morphology and desilting performance of diversions with different configurations

Experimental Set-Up and Procedure

Data Processing

Bed Morphology

Data Presentation

Turbulent Kinetic Energy

Conclusions