Turbulent Characteristics in an Egg-Shaped Orifice Fishway and a Comparison with a Rectangular Orifice

Abstract

A fishway can assist fish species in overcoming barriers to migration, which depends on the eco-hydraulic characteristics of the fishway. Based on the tail fish benefiting when at the rear of a school than when at the front, and taking into account most anadromous fish species being characterized by egg-shaped morphology, the turbulent characteristics of an egg-shaped orifice fishway were experimentally studied in a fishway flume, a comparison with a rectangular orifice fishway with the same aspect ratio was made. The results showed that the maximum longitudinal velocity for the egg-shaped orifice decays faster than that for the rectangular one, the longitudinal velocity profile exhibits two peak values, while the corresponding velocity distribution for the rectangular orifice only reveals one peak, peak values of turbulence intensity on the different horizontal plane of egg-shaped orifice occur in the orifice edges, the larger turbulence intensities still exists in the central besides the edges for the rectangular orifice, Reynolds stress reaches peak value at the orifice edges, Auto-correlation coefficient of longitudinal velocity within orifice region is of small amplitude and short period relative to the outside the orifice region, microscale eddies within the orifice region were larger than those outside, mean scale of eddy is of larger variation and shorter period, and develops outside the orifice region, frequency-spectrum of velocity fluctuation exhibits dominant frequency in the low-frequency domain.

Keywords

Fishway / Egg-shaped orifice / Rectangular orifice / Three-dimensional velocity / Velocity vector field / Turbulence intensity / Reynolds stress / Correlation function / Turbulence scale

Acknowledgments

We would like to express our sincere grateful to C. Liu for his assistance during the experimentation.

Author Contributions

Conceptualization, Z.D.; Methodology, L.C.; Software, L.C. and Z.H.; Validation, Z.G., Z.H. and Z.D.; Formal Analysis, L.C.; Investigation, L.C.; Resources, Z.D. and Z.G.; Data Curation, Z.D.; Writing—Original Draft Preparation, L.C.; Writing—Review & Editing, L.C. and Z.G.; Visualization, L.C. and Z.H.; Supervision, Z.D. and Z.G.

Ethics Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Funding

This study was financially supported by the National Natural Science Foundation of China (NSFC) [grant number 51779225].

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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