Flow Field Inside and Around a Square Fish Cage Considering Fish School Swimming Pattern

2021 ◽  
Author(s):  
Shuchuang Dong ◽  
Sang-gyu Park ◽  
Jinxin Zhou ◽  
Qiao Li ◽  
Takero Yoshida ◽  
...  
Keyword(s):  
Flow Field ◽  
Drag Force ◽  
Current Speed ◽  
Swimming Behavior ◽  
School Structure ◽  
Fish Swimming ◽  
Farmed Fish ◽  
Fish Schools ◽  
Fish School ◽  
Swimming Pattern

Abstract The interaction between fluid and fish cage with stocked fish is extremely complex, including fluid and structure, as well as fluid and fish swimming behavior. The on-current swimming pattern of fish schools was found toward the incoming flow in the previous laboratory studies, which is different from the circular swimming pattern commonly observed in the farming site. In this study, a pseudo fish school structure model (PFS) was proposed to reproduce the five circular swimming patterns of farmed yellowtail, and to investigate the influence of fish school behaviors on the flow field inside and around a model square fish cage in laboratory experiments. The results showed that the drag force acting on the square fish cage increased with the increase of the current speed for all fish school swimming patterns, but no clear difference was observed between the fish school swimming behavior patterns. Overall, the drag force of the square fish cage considering the farmed fish behavior decreased by 11.8%, compared to the drag force of the fish cage without PFS. The current speeds inside and downstream of the fish cage increased almost linearly with increasing current velocities. Compared with the case of the fish cage without PFS, the current speed inside the cage under motionless closely PFS (C0), revolving closely PFS (CR), motionless loosely PFS (L0) and revolving loosely PFS (LR) conditions changed by 10.8%, 9.4%, 65.8% and 39.7%, respectively. In addition, compared to the case of the fish cage without PFS, the current speeds under C0, CR, L0 and LR conditions decreased by 89.8%, 16.3%, 58.2%, and 31.9%, respectively, at 16.0cm downstream from the fish cage, and decreased by 69.2%, 19.4%, 62.7% and 26.3%, respectively, at 63.6cm downstream from the fish cage. Furthermore, the current speed distribution and relative horizontal turbulence intensity distribution inside and around the fish cage under different fish school swimming pattern was discussed. In the future, we will use live fish to conduct experiments to evaluate fish school models.

scholarly journals Effect of Cutting Ratio and Catch on Drag Characteristics and Fluttering Motions of Midwater Trawl Codend

2021 ◽  
Vol 9 (3) ◽  
pp. 256
Author(s):  
Wei Liu ◽  
Hao Tang ◽  
Xinxing You ◽  
Shuchuang Dong ◽  
Liuxiong Xu ◽  
...  
Keyword(s):  
Drag Force ◽  
Mesh Size ◽  
Current Speed ◽  
Midwater Trawl ◽  
Minimum Drag ◽  
Fish Catch ◽  
Spatial Geometry ◽  
By Catch ◽  
Trawl Fisheries ◽  
Crucial Part

The codend of a trawl net is the rearmost and crucial part of the net for selective fish catch and juvenile escape. To ensure efficient and sustainable midwater trawl fisheries, it is essential to better understand the drag characteristics and fluttering motions of a midwater trawl codend. These are generally affected by catch, cutting ratio, mesh size, and twine diameter. In this study, six nylon codend models with different cutting ratios (no cutting, 6:1, 5:1, 4:1, 7:2, and 3:1) were designed and tested in a professional flume tank under two conditions (empty codends and codends with catch) and five current speeds to obtain the drag force, spatial geometry, and movement trend. As the cutting ratio of empty codends decreased, the drag force decreased, and the drag coefficient increased. The unfolding degree of codend netting and the height of empty codends were found to be directly proportional to the current speed and inversely proportional to the cutting ratio. The positional amplitude of codend with cutting ratio 4:1 was the smallest for catch. The drag force of codends with catch increased as the current speed increased, and first decreased and then increased as the cutting ratio decreased. To ensure the best stability and minimum drag force of the codend, it is recommended to use the 4:1 cutting ratio codend.

Dynamic Response Analysis of Submarine Pipeline under Action of Current

2014 ◽  
Vol 1061-1062 ◽  
pp. 767-770
Author(s):  
Fan Lei ◽  
Yu Lin Deng ◽  
Xiao Hua Zhao
Keyword(s):  
Finite Element ◽  
Flow Field ◽  
Dynamic Response ◽  
Drag Force ◽  
Response Analysis ◽  
Vibration Characteristic ◽  
Submarine Pipeline ◽  
Structure Interaction ◽  
Finite Element Software ◽  
Distribution Of Flow

It’s important to study the vibration characteristic of submarine pipelines under current for reducing the harmful vibration. Research on fluid-structure interaction of submarine pipeline under current was presented. The pressure and velocity distribution of flow field around pipe with different velocity of flow were studied by ANSYS finite element software. The results show that the pipe is under the action of drag force along the direction of flow. The drag force increases with the flow velocity.

Growth and translation of a liquid-vapour compound drop in a second liquid. Part 1. Fluid mechanics

1989 ◽  
Vol 209 ◽  
pp. 617-637 ◽  
Author(s):  
S. T. Vuong ◽  
S. S. Sadhal
Keyword(s):  
Flow Field ◽  
Drag Force ◽  
Transfer Problem ◽  
Exact Analytical Solution ◽  
Fluid Motion ◽  
Axisymmetric Flow ◽  
Solid Sphere ◽  
Immiscible Liquid ◽  
Dispersed Phase ◽  
Spherical Drop

The fluid dynamics associated with a compound drop consisting of a vapour bubble, partly surrounded by its own liquid in another immiscible liquid is considered. The fluid motion is analysed in the limit of Stokes flow and at the same time the surface tension forces are considered to be large enough to allow the interfaces to have uniform curvature. The flow field consists of translation and growth that can arise from change of phase.An exact analytical solution for the axisymmetric flow field is obtained. The important results of physical interest are the drag force and the flow behaviour. In the case without growth, the drag force lies between the bubble and the solid-sphere limits for a sphere of the same volume as the total liquid and vapour dispersed phase. The maximum drag force is observed when the liquid and vapour volumes are nearly the same. This is the effect of weak circulation due to the smaller available space as compared with a spherical drop. With growth this effect appears to be enhanced. The flow streamlines exhibit secondary vortices in the dispersed phase when there is growth. The velocity field and the drag results here are applied to the heat transfer problem for the compound drop in Part 2 of this two-part series.

scholarly journals Bags-of-Features for fish school cluster characterization in pelagic ecosystems: application to the discrimination of juvenile and adult anchovy (Engraulis ringens) clusters off Peru

2012 ◽  
Vol 69 (8) ◽  
pp. 1329-1339 ◽  
Author(s):  
Ronan Fablet ◽  
Paul Gay ◽  
Salvador Peraltilla ◽  
Cecilia Peña ◽  
Ramiro Castillo ◽  
...  
Keyword(s):  
Data Sets ◽  
Correct Classification ◽  
Classification Rate ◽  
Fish Schools ◽  
Fish School ◽  
Acoustic Data ◽  
School Based ◽  
Engraulis Ringens ◽  
Fisheries Acoustics

Whereas fisheries acoustics data processing mainly focused on the detection, characterization, and recognition of individual fish schools, here we addressed the characterization and discrimination of fish school clusters. The proposed scheme relied on the application of the Bags-of-Features (BoF) approach to acoustic echograms. This approach is widely exploited for pattern recognition issues and naturally applies here, considering fish schools as the relevant elementary objects. It relies on the extraction and categorization of fish schools in fisheries acoustic data. Echogram descriptors were computed per unit echogram length as the numbers of schools in different school categories. We applied this approach to the discrimination of juvenile and adult anchovy ( Engraulis ringens ) off Peru. Whereas the discrimination of individual schools is low (below 70%), the proposed BoF scheme achieved between 89% and 92% of correct classification of juvenile and adult echograms for different survey data sets and significantly outperformed classical school-based echogram characteristics (about 10% of improvement of the correct classification rate). We further illustrate the potential of the proposed scheme for the estimation of the spatial distribution of juvenile and adult anchovy populations.

scholarly journals Aerodynamic performances of rounded fastback vehicle

2017 ◽  
Vol 231 (9) ◽  
pp. 1211-1221 ◽  
Author(s):  
Giacomo Rossitto ◽  
Christophe Sicot ◽  
Valérie Ferrand ◽  
Jacques Borée ◽  
Fabien Harambat
Keyword(s):  
Flow Field ◽  
Drag Force ◽  
Minor Effect ◽  
Near Wake ◽  
Vorticity Distribution ◽  
Aerodynamic Performances ◽  
Drag And Lift ◽  
A Minor ◽  
Yaw Angle

Experimental and numerical analyzes were performed to investigate the aerodynamic performances of a realistic vehicle with a different afterbody rounding. This afterbody rounding resulted in a reduction to drag and lift at a yaw angle of zero, while the crosswind performances were degraded. Rounding the side pillars generated moderate changes to the drag and also caused important lift reductions. A minor effect on the drag force was found to result from the opposite drag effects on the slanted and vertical surfaces. The vorticity distribution in the near wake was also analyzed to understand the flow field modifications due to the afterbody rounding. Crosswind sensitivity was investigated to complete the analysis of the aerodynamic performances of the rounded edges models. Additional tests were conducted with geometry modifications as spoilers and underbody diffusers.

Numerical Investigation of Gap to Diameter Ratio Effects on Flow Pattern and Drag Force Around Offshore Pipeline

2008 ◽  
Author(s):  
Mohammad Hossein Kazeminezhad ◽  
Abbas Yeganeh Bakhtiary ◽  
Amir Etemad-Shahidi ◽  
Reza Valipour
Keyword(s):  
Flow Field ◽  
Flow Pattern ◽  
Drag Force ◽  
Vortex Shedding ◽  
Diameter Ratio ◽  
Turbulence Closure ◽  
Navier Stokes ◽  
Hydrodynamic Coefficient ◽  
Gap Ratio ◽  
Offshore Pipeline

Offshore pipelines are exposed to hydrodynamic forces due to the current actions. The forces (drag and lift) have an unsteady nature and oscillate around their average values because of the occurrence of vortex shedding behind the pipeline. Vortex shedding leads to the Vortex-Induced-Vibration (VIV) which is an important source of fatigue damage of pipeline in free spanning sections. Time-averaged drag force can be calculated using drag equation which has a hydrodynamic coefficient. However it does not take the VIV effects into account. To do so and to consider the unsteady nature of the force, the flow pattern and vortex shedding phenomenon around a pipeline should be simulated accurately. The main objective of this study is to simulate the flow field around an offshore pipeline placed on the plane bed. This study investigates the gap ratio effects on the flow pattern and drag force exerted on the pipeline as well. The flow field was simulated by the two dimensional Reynolds-Averaged Navier-Stokes (RANS) equations with a k-ε turbulence closure model. Results indicate that the k-ε turbulence closure can simulate the vortex shedding behind a pipeline and the oscillation of drag force successfully. By considering different values of gap to diameter ratio, it is found that the drag coefficient is increased gradually as the gap ratio rises up and the increase rate reduces as gap ratio increases.

scholarly journals The effect of hypoxia on fish schooling

2017 ◽  
Vol 372 (1727) ◽  
pp. 20160236 ◽  
Author(s):  
Paolo Domenici ◽  
John F. Steffensen ◽  
Stefano Marras
Keyword(s):  
Climate Change ◽  
Multiple Stressors ◽  
Maximum Size ◽  
School Structure ◽  
Fish Behaviour ◽  
Low Oxygen ◽  
Fish Schools ◽  
Hypoxic Conditions ◽  
Trade Offs ◽  
Schooling Behaviour

Low-oxygen areas are expanding in the oceans as a result of climate change. Work carried out during the past two decades suggests that, in addition to impairing basic physiological functions, hypoxia can also affect fish behaviour. Given that many fish species are known to school, and that schooling is advantageous for their survival, the effect of hypoxia on schooling behaviour may have important ecological consequences. Here, we review the effects of hypoxia on school structure and dynamics, together with the mechanisms that cause an increase in school volume and that ultimately lead to school disruption. Furthermore, the effect of hypoxia generates a number of trade-offs in terms of schooling positions and school structure. Field observations have found that large schools of fish can exacerbate hypoxic conditions, with potential consequences for school structure and size. Therefore, previous models that predict the maximum size attainable by fish schools in relation to oxygen levels are also reviewed. Finally, we suggest that studies on the effect of hypoxia on schooling need to be integrated with those on temperature and ocean acidifications within a framework aimed at increasing our ability to predict the effect of multiple stressors of climate change on fish behaviour. This article is part of the themed issue ‘Physiological determinants of social behaviour in animals’.

Neuronal elements that mediate escape swimming and suppress feeding behavior in the predatory sea slug Pleurobranchaea

1995 ◽  
Vol 74 (5) ◽  
pp. 1900-1910 ◽  
Author(s):  
J. Jing ◽  
R. Gillette
Keyword(s):  
Feeding Behavior ◽  
Spike Activity ◽  
Feedback Inhibition ◽  
Swimming Behavior ◽  
Pattern Generation ◽  
The Body ◽  
Noxious Stimulation ◽  
Swimming Pattern ◽  
Dorsal Flexion ◽  
Stimulation Of

1. The white, bilaterally paired A1 interneurons of the cerebropleural ganglion of Pleurobranchaea californica fire rhythmic bursts of action potentials during escape swimming behavior. We studied the role of the A1s in swimming behavior and pattern generation in whole animal and isolated CNS preparations. 2. The escape swim is a cyclic sequence of dorsal and ventral flexions of the body. During the swim, A1 bursts precede and accompany the dorsal flexion phase of the cycle. Hyperpolarization of A1 to prevent spike activity interrupts swimming behavior in the whole animal and fictive swimming in the isolated CNS. Stimulated A1 activity was not observed to cause swimming in whole animals, and was only occasionally sufficient to trigger fictive swimming activity in the isolated CNS. 3. In quiescent whole animal preparations, stimulation of a single A1 normally causes a single dorsal flexion followed by body flexion to the side contralateral to the stimulated cell; characteristically, A1 spike activity stimulates feedback inhibition coinciding with the end of dorsal flexion and the onset of contralateral flexion. 4. A1 spike activity suppresses feeding behavior and causes proboscis retraction in whole animal preparations induced to feed. A1 activity also suppresses fictive feeding driven by stimulation of the critical phasic paracerebral neurons (PCps) of the motor network of feeding in the isolated CNS. Concomitantly, A1 spikes cause potent inhibition of the PCp interneurons. 5. The A1s are specifically excited by noxious mechanical and chemical stimuli, but are not affected by feeding stimuli or the occurrence of feeding behavior. 6. We conclude that the A1 neurons are elements of an escape swimming pattern generator, and that they are probably homologous to the similar C2 neurons of the nudibranch Tritonia diomedea. One of their functions outside of generating the swim pattern may be the suppression of feeding behavior in response to noxious stimulation. These observations provide a neural mechanism for the original observations of the dominance of escape swimming behavior over feeding.

Olfaction and Vision in Fish Schooling

1966 ◽  
Vol 45 (3) ◽  
pp. 449-464
Author(s):  
C. C. HEMMINGS
Keyword(s):  
Visual Images ◽  
School Structure ◽  
Visual Response ◽  
Short Term ◽  
Linear Gradient ◽  
Fish School ◽  
Schooling Behaviour ◽  
Clear Plastic ◽  
Repulsive Forces

1. The behaviour of individual roach was observed in a horizontal linear gradient of species odour. No attempt was made to analyse the odour involved. 2. The behaviour of roach, grey mullet and Chromis was studied in the presence of (a) a mirror, or (b) a second fish behind a clear plastic sheet. 3. Roach showed nearly as strong a response to attractant species odour as to the repellent ‘Schreckstoff’. The relative strengths of responses to directional visual images and non-directional odour gradients were compared. 4. Short-term and long-term declines in the strength of the response to odour occurred. 5. Observation of a ‘two-fish school’ suggested that a system of exploratory, returning and following tendencies co-ordinated schooling behaviour. 6. Isolation of roach for a period of 20-25 weeks caused enhancement of the olfactory reaction but completely disrupted the visual response. 7. It is suggested that school structure is maintained by balanced attractive and repulsive ‘forces’; the attraction modalities involved are vision by day and olfaction by night, and the repulsion modality is the lateral line sense.

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