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Turbulent flow interacting with flexible trawl net structure including simulation catch in flume tank
Bruno Thierry Nyatchouba Nsangue1,2,3,4,5, Hao Tang6,7,8,9,10, Wei Liu1
1College of Marine Sciences, Shanghai Ocean University, 999 Huchenghuan Road, Lingang New District, Shanghai, 201306, People's Republic of China.
Scientific Reports
|April 17, 2023
Summary
The presence of fish catch in midwater trawls significantly alters fluid dynamics, increasing turbulence and causing net fluttering. This complex fluid-structure interaction impacts fishing gear performance and selectivity.
Area of Science:
- Fluid dynamics
- Fisheries engineering
- Turbulence modeling
Background:
- Understanding fluid-trawl interaction is crucial for drag force, structural behavior, and selectivity prediction.
- Midwater trawls experience complex interactions with fluid flow and stocked catches.
Purpose of the Study:
- To assess turbulent characteristics inside and around midwater trawls with and without catch.
- To analyze the impact of catch presence on trawl fluttering and flow dynamics.
Main Methods:
- Utilized 3D electromagnetic current velocity meter measurements on a 1/35 scaled midwater trawl model.
- Analyzed time-averaged flow velocity fields and turbulent parameters.
- Performed Fourier analysis on flow velocities, trawl motion, turbulent kinetic energy, and momentum flux.
Main Results:
- Catch presence induces significant trawl fluttering, affecting flow passage.
- Flow velocities inside/around the net with catch were 12.41% lower than without catch.
- Turbulent length scale and Reynolds number increased by 33.05% with catch, indicating enhanced turbulence.
Conclusions:
- Catch significantly impacts unsteady turbulent flow and causes trawl fluttering.
- Fluid-structure interaction is complex: trawl motion affects flow, and turbulent flow influences trawl motion.
- Findings are essential for improving midwater trawl design and selectivity.
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