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Article

Flow Turbulence Characteristics and Mass Transport in the Near-Wake Region of an Aquaculture Cage Net Panel

1
State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China
2
Tang Scholar, Beijing Normal University, Beijing 100875, China
3
School of Science and Engineering, University of Dundee, Dundee DD1 4HN, UK
4
Department of Civil and Environmental Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA
5
Department of Civil, Architectural and Environmental Engineering, University of Naples Federico II, 80125 Napoli, Italy
*
Authors to whom correspondence should be addressed.
Academic Editor: Jose G. Vasconcelos
Water 2021, 13(3), 294; https://doi.org/10.3390/w13030294
Received: 21 December 2020 / Revised: 19 January 2021 / Accepted: 21 January 2021 / Published: 25 January 2021
(This article belongs to the Special Issue Advances in Environmental Hydraulics)
Cage-based aquaculture has been growing rapidly in recent years. In some locations, cage-based aquaculture has resulted in the clustering of large quantities of cages in fish farms located in inland lakes or reservoirs and coastal embayments or fjords, significantly affecting flow and mass transport in the surrounding waters. Existing studies have focused primarily on the macro-scale flow blockage effects of fish cages, and the complex wake flow and associated near-field mass transport in the presence of the cages remain largely unclear. As a first step toward resolving this knowledge gap, this study employed the combined Particle Image Velocimetry and Planar Laser Induced Fluorescence (PIV-PLIF) flow imaging technique to measure turbulence characteristics and associated mass transport in the near wake of a steady current through an aquaculture cage net panel in parametric flume experiments. In the near-wake region, defined as ~3M (mesh size) downstream of the net, the flow turbulence was observed to be highly inhomogeneous and anisotropic in nature. Further downstream, the turbulent intensity followed a power-law decay after the turbulence production region, albeit with a decay exponent much smaller than reported values for analogous grid-generated turbulence. Overall, the presence of the net panel slightly enhanced the lateral spreading of the scalar plume, but the lateral distribution of the scalar concentration, concentration fluctuation and transverse turbulent scalar flux exhibited self-similarity from the near-wake region where the flow was still strongly inhomogeneous. The apparent turbulent diffusivity estimated from the gross plume parameters was found to be in reasonable agreement with the Taylor diffusivity calculated as the product of the transverse velocity fluctuation and integral length scale, even when the plume development was still transitioning from a turbulent-convective to turbulent-diffusive regime. The findings of this study provide references to the near-field scalar transport of fish cages, which has important implications in the assessment of the environmental impacts and environmental carrying capacity of cage-based aquaculture. View Full-Text
Keywords: aquaculture cages; fishing net panel; near wake; turbulence characteristics; mass transport; PIV-PLIF aquaculture cages; fishing net panel; near wake; turbulence characteristics; mass transport; PIV-PLIF
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MDPI and ACS Style

Shao, D.; Huang, L.; Wang, R.-Q.; Gualtieri, C.; Cuthbertson, A. Flow Turbulence Characteristics and Mass Transport in the Near-Wake Region of an Aquaculture Cage Net Panel. Water 2021, 13, 294. https://doi.org/10.3390/w13030294

AMA Style

Shao D, Huang L, Wang R-Q, Gualtieri C, Cuthbertson A. Flow Turbulence Characteristics and Mass Transport in the Near-Wake Region of an Aquaculture Cage Net Panel. Water. 2021; 13(3):294. https://doi.org/10.3390/w13030294

Chicago/Turabian Style

Shao, Dongdong, Li Huang, Ruo-Qian Wang, Carlo Gualtieri, and Alan Cuthbertson. 2021. "Flow Turbulence Characteristics and Mass Transport in the Near-Wake Region of an Aquaculture Cage Net Panel" Water 13, no. 3: 294. https://doi.org/10.3390/w13030294

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