Study of a Rock-Ramp Fish Pass with Staggered Emergent Square Obstacles

Flavia Cavalcanti Miranda,Tien Dung Tran,Ludovic Cassan,Pascale Laurens

doi:10.3390/w13091175

Flavia Cavalcanti Miranda, Tien Dung Tran + Show 2 more

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https://doi.org/10.3390/w13091175

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Abstract

A rock-ramp fish passage with square obstacles was experimentally and numerically studied in this work with the objective of investigating in detail the hydraulic behind such fishways and to evaluate the importance of the shape of the obstacles. The LES and VOF methods were used for the simulations, and for the measurements, shadowgraphy and ADV were applied. Two different validations were successfully performed. In the first one, the experimental and numerical results of a chosen case were compared in detail. In the second validation, the focus was given to the stage-discharge. Following the validation, a numerical study was carried out to point out the differences in the flow characteristics from a configuration with square and circular obstacles. The discharge was nearly the same for both configurations, which implies different water depths. The results showed a lower velocity field, lower turbulent kinetic energy, and lower lateral fluctuations for the configuration with square blocks, which indicated a better passability for this geometry. However, it also presented a higher water depth, which led to a less attractive discharge. The differences in the flow generated in the two configurations indicated that the shape is an important modifiable parameter to be considered in the design process.

Highlights

The present paper studied a rock-ramp-type fish pass and was based on the channel studied by Cassan et al [2] and Chorda et al [1]
The experimental measurements of velocity profiles were performed with an acoustic Doppler velocimeter (ADV) with a 3D downlooking probe in which the three velocity components were captured at a frequency of 50 Hz over 180 s
A rock-ramp fish pass with square blocks was experimentally and numerically investigated

Summary

Introduction

Rock-ramp fish passes are an economical and ecological alternative to unobstructed fish migrations and contribute to the good ecological condition of the rivers. They generally consist of a sloped bottom in which obstacles are staggered, arranged with the objective of providing energy dissipation and reducing flow velocity [1,2]. The obstacles provide resting places for fishes swimming upstream [3] This type of passage is especially interesting due to the high flow, which enhances the attractiveness for fish and decreases the risk of clogging (large spacing between blocks) and silting (no pool) [2]

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