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Research Papers: Ocean Space Utilization

Structural Analysis of Aquaculture Nets: Comparison and Validation of Different Numerical Modeling Approaches

[+] Author and Article Information
Heidi Moe-Føre

SINTEF Fisheries and Aquaculture,
Postboks 4762 Sluppen,
Trondheim 7465, Norway
e-mail: Heidi.Moe.Fore@sintef.no

Per Christian Endresen

SINTEF Fisheries and Aquaculture,
Postboks 4762 Sluppen,
Trondheim 7465, Norway
e-mail: Per.Christian.Endresen@sintef.no

Karl Gunnar Aarsæther

SINTEF Fisheries and Aquaculture,
Postboks 4762 Sluppen,
Trondheim 7465, Norway
e-mail: Karl.Gunnar.Aarsather@sintef.no

Jørgen Jensen

SINTEF Fisheries and Aquaculture,
Postboks 4762 Sluppen,
Trondheim 7465, Norway
e-mail: Jorgen.Jensen@sintef.no

Martin Føre

SINTEF Fisheries and Aquaculture,
Postboks 4762 Sluppen,
Trondheim 7465, Norway
e-mail: Martin.Fore@sintef.no

David Kristiansen

SINTEF Fisheries and Aquaculture,
Postboks 4762 Sluppen,
Trondheim 7465, Norway
e-mail: David.Kristiansen@sintef.no

Arne Fredheim

SINTEF Fisheries and Aquaculture,
Postboks 4762 Sluppen,
Trondheim 7465, Norway
e-mail: Arne.Fredheim@sintef.no

Pål Lader

SINTEF Fisheries and Aquaculture,
Postboks 4762 Sluppen,
Trondheim 7465, Norway
e-mail: Pal.Lader@sintef.no

Karl-Johan Reite

SINTEF Fisheries and Aquaculture,
Postboks 4762 Sluppen,
Trondheim 7465, Norway
e-mail: Karl.Johan.Reite@sintef.no

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received August 25, 2014; final manuscript received March 26, 2015; published online April 16, 2015. Assoc. Editor: Hideyuki Suzuki.

J. Offshore Mech. Arct. Eng 137(4), 041201 (Aug 01, 2015) (7 pages) Paper No: OMAE-14-1114; doi: 10.1115/1.4030255 History: Received August 25, 2014; Revised March 26, 2015; Online April 16, 2015

The performance of three different numerical methods were compared and evaluated against data from physical model tests of nets subjected to a static load due to water currents. A parameter study of a simplified net cage model subjected to a steady flow was performed by all methods, varying the net solidity and the flow velocity. The three numerical methods applied models based on springs, trusses, or triangular finite elements. Hydrodynamic load calculations were based on the drag term in Morison's equation and the cross-flow principle. Different approaches to account for wake effects were applied. In general, the presented numerical methods should be able to calculate loads and deformations within acceptable tolerance limits for low to intermediate current flow velocities and net solidities, while numerical analyses of high solidity nets subjected to high current velocities tend to overpredict the drag loads acting on the structure. To accurately estimate hydrodynamic loads and structural response of net structures with high projected solidity, new knowledge and methods are needed.

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References

Standards Norway, 2009, NS 9415 Marine Fish Farms—Requirements for Site Survey, Risk Analyses, Design, Dimensioning, Production, Installation and Operation.
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The International Organization for Standardization, 2002, ISO 1107 Fishing Nets—Netting – Basic Terms and Definitions.
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Moe, H., 2009, “Strength Analysis of Net Structures,” Ph.D. thesis, 2009:48, Norwegian University of Science and Technology, Norway.
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Figures

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Fig. 1

Physical model test setup (N19, Table 1)

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Fig. 2

Unloaded triangle model (elements are visualized with a grid simulating the netting structure)

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Fig. 3

Submerged truss model with bottom weights

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Fig. 4

Triangle model N30 subjected to a uniform flow, v = 0.50 m/s

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Fig. 5

Truss model N30 subjected to a uniform flow, v = 0.50 m/s

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Fig. 6

Global deformation of the numerical models with various solidities subjected to various flow velocities

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Fig. 7

Calculated and measured drag and lift forces. The numerical results are named by their element type (triangle, truss, and spring). (a)–(c) Forces are given as a function of flow velocity for different solidities (Sn). (d)–(f) Forces are given as a function of solidity for different flow velocities (v).

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Fig. 8

Comparison of shape of physical model and modified truss method model subjected to v = 0.5 m/s

Tables

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