Unsteady turbulent flow developing inside and around different parts of fluttering trawl net in flume tank

Thierry, Nyatchouba Nsangue Bruno; Tang, Hao; Achille, Njomoue Pandong; Xu, Liuxiong; Hu, Fuxiang

doi:10.1016/j.jfluidstructs.2021.103451

Cited by 14 publications

(12 citation statements)

References 37 publications

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“…The measurements were performed at a fixed streamwise velocity of 0.36 m/s, a door spread of 1.8 m, and with a turbulence level of 5%. This turbulence level corresponded to the one computed in a flume tank without fishing gear where the flow was uniform 23 , 36 . Using Reynolds decomposition, the turbulence level has been determined and it is of an order of 4.63%.…”

Section: Methodssupporting

confidence: 64%

“…Using Reynolds decomposition, the turbulence level has been determined and it is of an order of 4.63%. During the flow measurement, the turbulent boundary layer developed around the side wall of the flume tank did not affect the measurement of the flow field on the different points inside and around the trawl net as confirmed by Thierry et al 23 for the bottom trawl or Jonsson et al 37 on the analysis of the hydrodynamic characteristics on 12 different benthic biological flumes. The flow meter (propeller tachometer) was placed at 1.2 m directly in front of the trawl mouth to detect the current flow velocity.…”

Section: Methodsmentioning

confidence: 66%

“…This analysis provides a better understanding of the flow behavior and oscillatory motions of the trawl net, thus affords relevant information for the analysis of hydrodynamic forces and selectivity via the fish response, such as the herding response or escape behavior 10 , 14 . Indeed, the fluid flow loads inside and around a trawl net structure can be clarified in static and dynamic loads, and are directly related to its elastic and dynamic instabilities 13 , 23 . The former is due to the vertical dynamic pressure variation of the flow fields along with the trawl structure, and the latter is associated with pressure and velocity fluctuations due to the vortex shedding, turbulent boundary layer, and the turbulent flow in the trawl wake.…”

Section: Introductionmentioning

confidence: 99%

“…Then, they adopted a hybrid volume method (HVM) to model the fluid–structure interaction between the net and surrounding water. Thierry et al 6 , 23 analyzed the behavior of the turbulent flow developing inside and around the bottom trawl based on the numerical simulation and flume tank experiment. They found that the trawl motions linked to this turbulent flow considerably modified the opening and the geometrical shape of the mesh component on the trawl net, which then strongly influenced the spatial and temporal fluctuations of the selected performance parameters of the trawl net.…”

Section: Introductionmentioning

confidence: 99%

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Turbulent flow interacting with flexible trawl net structure including simulation catch in flume tank

Thierry

Tang

Liu

et al. 2023

Sci Rep

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The interaction between fluid and the midwater trawl with stocked catches is extremely complex, but essential to improve the understanding of the drag force acting on the trawl, the behavior of the fishing structure during a trawling process, and to predict its selectivity process. The present study assesses the turbulent characteristics inside and around the midwater trawls with catch and without catch linked to its fluttering motion. The analysis is based on three-dimensional electromagnetic current velocity meter measurements performed in the multiple points inside and outside different parts of a 1/35 scaled midwater trawl model with the aim of access the main turbulent flow structure inside and around the gear. Time-averaged normalized flow velocity fields and turbulent flow parameters were analyzed from the measured flow data. Furthermore, Fourier analysis was conducted by watching the time–frequency Power spectrum content of instantaneous flow velocities fields, the fluttering trawl motions, turbulent kinetic energy, and momentum flux. Based on successive analyzes of mean flow characteristics and turbulent flow parameters, it has been demonstrated that the presence of catch inside the trawl net impacts the evolution of unsteady turbulent flow by creating large trawl fluttering motions that strongly affect the flow passage. The results showed that the time-averaged normalized streamwise and transverse flow velocities inside and around the trawl net with catch were 12.41% lower compared with that obtained inside and around the trawl without catch. The turbulent length scale and turbulent Reynolds number obtained in the different part of the trawl net with catch were about 33.05% greater than those obtained on the trawl net without catch, confirming that the unsteady turbulent flow developing inside and around the midwater trawl is influence by the catch and liner. It is observed that the motions of both the trawl without catch and the trawl with catch are mainly of a low-frequency activity and another component related to unsteady turbulent flow street. A complex fluid–structure interaction is then demonstrated where the fluttering motions of the trawl net affect the fluid flow inside and around trawl net, the fluid force, turbulent pattern, and simultaneously, the periodic unsteady turbulent flow influence the trawl motions.

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Section: Methodssupporting

confidence: 64%

Section: Methodsmentioning

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Turbulent flow interacting with flexible trawl net structure including simulation catch in flume tank

Thierry

Tang

Liu

et al. 2023

Sci Rep

Self Cite

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“…The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has set precautionary catch limits and catch quotas for the sustainable exploitation of Antarctic krill in order to ensure ecosystem equilibrium, the sustainability of krill fisheries, and to balance the competing interests of Antarctic krill (Wan et al, 2019;Bairstow et al, 2021). Furthermore, the Antarctic krill fisheries also face too many issues such as gear selectivity, energy efficiency, catchability, and ecological sustainability (Wan et al, 2019;Thierry et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

Flume Tank Evaluation on the Effect of Liners on the Physical Performance of the Antarctic Krill Trawl

et al. 2022

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The Antarctic krill (Euphausia superba) is one of the most abundant resources in the ocean, which provides food for several important species in the Antarctic Ocean, and is targeted commercially by humans for many decades. To sustainably manage and harvest the species, energy-efficient, catch-efficient, and selective fishing gears should be developed for the Antarctic krill trawl fishery. This study investigates the effect of twine area and the liner length on the engineering performance of trawl through flume tank testing of trawl model to predict the performance of the full-scale midwater trawl used in the Antarctic krill fishery. Four 1/35th scale trawl model nets with varying lengths of the liner, based on the traditional trawl used in the Antarctic krill fishery, were designed using modified Tauti’s law and were tested in a flume tank at different towing speed, door spread, heavy bob weight, and the ratio of buoyancy to the fishing line (F/G). The results showed that the reduction in liner length by 25 and 50% from the traditional trawl net led to the decrease in twine area by 11.01 and 19.31% and, consequently, resulted in reductions in the lower bridle tension by 12.44 and 19.78%, and increases in energy efficiency by 17.98 and 25.73%, respectively. In addition, the reduction in liner length by 25 and 50% were found to increase the net mouth opening by 2.63 and 5.38% and the swept area by 6.52 and 8.38%, respectively, both of which are proportional to catch rates. Although the trawl net with 50% liner length is more energy-efficient and large mouth opening than those of the trawl net with the liner length over 75% of the trawl body, the large mesh section without a liner can result in the escape of the krill from the trawl, reducing overall catch efficiency. We, therefore, recommend the trawl with 75% of liner length as a suitable design for Antarctic krill considering energy efficiency and catch efficiency.

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Revealing the Fluttering Motions of Mid-Water Trawl Codend Through Sea Trials: Case Study of Antarctic Krill Trawl Codend

Liu

Tang

Thierry

et al. 2023

J. Ocean Univ. China

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Unsteady turbulent flow developing inside and around different parts of fluttering trawl net in flume tank

Cited by 14 publications

References 37 publications

Turbulent flow interacting with flexible trawl net structure including simulation catch in flume tank

Turbulent flow interacting with flexible trawl net structure including simulation catch in flume tank

Flume Tank Evaluation on the Effect of Liners on the Physical Performance of the Antarctic Krill Trawl

Revealing the Fluttering Motions of Mid-Water Trawl Codend Through Sea Trials: Case Study of Antarctic Krill Trawl Codend

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