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Experimental Study on the Interaction Between the Net and the Weight System for a Gravity Type Fish Farm

[+] Author Affiliations
Pål Lader, David Kristiansen, Østen Jensen

SINTEF Fisheries and Aquaculture, Trondheim, Norway

David W. Fredriksson

United States Naval Academy, Annapolis, MD

Paper No. OMAE2013-11048, pp. V003T05A019; 10 pages
doi:10.1115/OMAE2013-11048
From:
  • ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering
  • Volume 3: Materials Technology; Ocean Space Utilization
  • Nantes, France, June 9–14, 2013
  • Conference Sponsors: Ocean, Offshore and Arctic Engineering Division
  • ISBN: 978-0-7918-5535-5
  • Copyright © 2013 by ASME

abstract

The escape of salmon from aquaculture farms is considered a major problem for the industry. Structural failure is the dominating cause for escapes. One major issue is the contact, and subsequent abrasion between the sinker tube chain and the net, which has caused several large-scale escapes over the past years. Model tests were performed in a tow tank at the United States Naval Academy to investigate at which combinations of waves and current the net deforms and comes in contact with the sinker tube chain. A model in scale 1:40 was used to represent a fish cage with a circumference of 120 meters and net depth of 40 meters. Building a physical model of such a compliant structure is inherently difficult, so particular attention was given to similarity issues. With the physical modelling approach, two different net design and four different weighting systems were tested. The experiments showed that the sinker tube with the fixed connection to the net performs better than individual weights both for cylindrical and conical nets. For cylindrical nets exposed to current only contact occurred at a velocity of 0.3 m/s when using weights and at a velocity of 0.5 m/s when using either the fixed or sliding sinker tube. The results for conical nets exposed to waves and current were less consistent. Weights (contact at 0.3 m/s) performed better than a sinker tube with sliding connection (contact due to waves only) but not as good as a fixed sinker tube (contact at 0.3 m/s). When exposed to waves and current contact occurred at a higher velocity and over a smaller area when using the conical net compared to the conventional cylindrical. For cylindrical nets contact occurred when exposed to waves alone, whereas for conical nets contact occurred at current velocities of 0 m/s, 0.15 m/s, and 0.3 m/s for the weights, the sliding sinker tube, and the fixed sinker tube respectively.

Copyright © 2013 by ASME

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