Research Papers

Comparison and Validation of Two Models of Netting Deformation

[+] Author and Article Information
F. G. O’Neill

 Fisheries Research Services Marine Laboratory, 375 Victoria Road, Aberdeen AB11 9DB, Scotland

D. Priour

 IFREMER, BP 70, Pointe du Diable, 29280 Plouzane Cedex, France

J. Appl. Mech 76(5), 051001 (Jun 16, 2009) (7 pages) doi:10.1115/1.3112737 History: Received January 14, 2008; Revised January 26, 2009; Published June 16, 2009

The predictions of two numerical models of the deformation of fishing netting are compared. Analytical solutions are found to the differential equations that govern one of these models, and these solutions are used to evaluate the accuracy of both. There is very good agreement between the numerical solutions and the corresponding analytical values. The models are also applied to the deformation of networks where there is an in-plane shear resistance. Although there are no analytical solutions available, the similarity of the numerical solutions gives confidence in both methods.

Copyright © 2009 by American Society of Mechanical Engineers
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Figure 1

A demersal otter trawl with the axisymmetric cod-end, at the back of the fishing gear, magnified

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Figure 2

The coordinate system and the strip of meshes under consideration along the profile of the axisymmetric cod-end

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Figure 3

The coordinate system and the in-plane membrane forces acting on one of the meshes along the network profile

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Figure 4

The triangular finite elements that discretize the netting in Priour’s model

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Figure 5

The forces and bending couple acting on a twine element of a reinforced network

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Figure 6

Tractrix calculated by Priour’s model. The radii of the boundary rings are 1 m and 0.048599 m. The distance between them is 4.6473 m. The mesh size of the netting is M=0.1 m, the number of meshes around N=100, and the number of meshes between the rings is L=50.

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Figure 7

The profile of a cod-end (axisymmetric network) subject to a constant internal pressure force acting over the first 8 m of the cod-end profile. The bold part of the curve identifies the region where the pressure acts. The cod-end specification is M=0.1 m, N=100, and L=200. The horizontal line is the upper bound on the radius.

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Figure 8

The maximum radius of a cod-end with M=0.1 m, N=100, and L=200, where the pressure force acts over a range from 3 m to 12 m. The solid line and the points are the predictions of the models of O’Neill and Priour, respectively. The dashed line is the analytical upper bound.

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Figure 9

The profiles predicted by models of O’Neill and Priour of a cod-end subject to a constant internal pressure. The bold part of each curve identifies the region where the pressure acts. The outer curve is the solution predicted by both models for the case there is no twine bending stiffness and cannot be differentiated graphically. The inner curves are the predictions where there is bending stiffness, which differs by about 5% where the cod-end necks.




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