Higher-Order Velocity Moments, Turbulence Scales and Energy Dissipation Rate around a Boulder in a Rock-Ramp Fish Passage

Amir Golpira,David Z. Zhu,Abul BM Baki

doi:10.3390/su12135385

Amir Golpira, David Z. Zhu + Show 1 more

Open Access

https://doi.org/10.3390/su12135385

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Journal: Sustainability	Publication Date: Jul 3, 2020
Citations: 9	License type: CC BY 4.0

Affiliation: Clarkson University, University of Alberta

Abstract

This experimental study investigated the higher-order velocity moments, turbulence time and length scales, and energy dissipation rates around an intermediately submerged boulder within a wake-interference flow regime in a rock-ramp fish passage. The results show a noticeable variation in the studied parameters in the wake of the boulder, as well as near the bed and boulder crest. The higher-order velocity moments show the presence of infrequent strong ejections downstream of the boulder, which may lead to higher sediment deposition and vertical mixing. The eddy length scales and the volumetric energy dissipation in this experimental model were discussed in relation to fish behavior for both the experimental model and a prototype. Relationships were proposed to roughly estimate integral length scales and energy dissipation rates around the boulder over the flow depth. The findings of this study may improve the design of rock-ramp fish passages considering the effects of turbulence on fish swimming performance and sediment transport.

Highlights

The fragmentation of rivers through the construction of hydraulic structures, such as dams and weirs, has widely interrupted the longitudinal connectivity of rivers, which is an important ecological dimension of aquatic habitats
Among numerous fish passage solutions, recent attempts have been made to enhance the design of nature-like fish passages, which are suitable for a wide variety of fish species due to their mimicking characteristics of natural channels such as substrate, slope and hydrodynamics [4,5]
In comparison with [12,29], this study focuses on a finer spatial grid around boulders with higher submergence ratios, which are more common in nature-like fish passages

Summary

Introduction

The fragmentation of rivers through the construction of hydraulic structures, such as dams and weirs, has widely interrupted the longitudinal connectivity of rivers, which is an important ecological dimension of aquatic habitats. To enhance the environmental sustainability of rivers, the construction of fish passages has been used as a common solution to re-establish river longitudinal connectivity. Among numerous fish passage solutions, recent attempts have been made to enhance the design of nature-like fish passages, which are suitable for a wide variety of fish species due to their mimicking characteristics of natural channels such as substrate, slope and hydrodynamics [4,5]. Rock-ramp fish passages have been used as an effective type of nature-like fish passage which enhances flow heterogeneity [6]. Understanding the effects of boulders on the surrounding flow is instrumental for an optimum nature-like fish passage design

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