umerical simulation of deformations and forces of a floating fish age collar in waves iao

The dynamic behavior of a fish cage collar in waves was investigated using a numerical model based on the finite element method. The floating collar and mooring system were divided into a series of line segments modeled by straight massless model segments with a node at each end. To verify the validity of the numerical model, research data from other authors were cited and compared with the simulated results, the comparison of results showed a good agreement. The numerical model was then applied to a dynamic simulation of a floating cage collar in waves to analyze its elastic deformation and mooring line tension. The simulated results indicated that the greatest deformation of the collar taken place in lastic deformation ooring line tension umerical simulation the position of the mooring line connection point when incident waves were in the same direction. An increase in the length of mooring line would help to decrease the mooring line tension of the collar. Furthermore, the effects of collar dimension, including collar circumference, pipe diameter in crosssection, and pipe thickness, on the dynamic behavior of the floating collar were discussed. The results of this study provided a better understanding of the dynamic behavior of the fish cage collar. © 2016 Elsevier B.V. All rights reserved. Introduction Commercial marine fish farming is becoming prevalent in the orld due to diminishing fishery resources in the ocean and ncreasing demand of sea products. As one of the main culture ethods, cage aquaculture plays an important role in marine fish arming in China, of which yield accounts for about 50% of marine sh farming. Marine cage aquaculture has become an alternative or future development of the fisheries industry in China. However, wing to the aggravation of near-shore pollution and occupation f the sea area for coastal industrialization and tourism, cage farmng locations need to be moved further offshore in exposed water. herefore, the safety performance and reliability of the fish cage nder the action of severe sea loads becomes the focus of attention. In an open-sea area, a fish cage exposed to strong waves and curent may deform to such a large extent that normal functionality is isabled. Therefore, extensive studies of hydrodynamic behaviors ∗ Corresponding author at: South China Sea Fisheries Research Institute, Chinese cademy of Fishery Sciences, No. 231 Xingangxi Road, Guangzhou 510300, China. E-mail address: huangx-hua@163.com (X.-H. Huang). ttp://dx.doi. org/10.1016/j.aquaeng. 2016.07. 003 144-8609/© 2016 Elsevier B.V. All rights reserved. of fish cages have been conducted over the recent years. For example, Lee et al. (2008) presented a mathematical model for analyzing the performance of a fish cage with a floating collar influenced by currents and waves. Huang et al. (2008) analyzed the effects of waves with a uniform current on marine aquaculture gravity-type cages using a numerical model validated by physical model tests. A risk analysis (Huang and Pan, 2010) and submergence characteristics (Shainee et al., 2013) of single-point mooring cage system in waves and current were conducted. Kristiansen and Faltinsen (2012, 2015) proposed and discussed a screen type of force model for the viscous hydrodynamic load on an aquaculture net cage. Fredriksson et al. (2007a) studied mooring system tensions of a large fish farm containing 20 net pens in the absence of waves, using a numerical model and field measurements. Zhao et al. (2009, 2013) conducted analysis of dynamic behavior of a box-shaped net cage and a column-shaped net cage in waves and current using a numerical model, based on the lumped mass method and the principle of rigid body kinematics. DeCew et al. (2013) reported that an acoustic method was utilized to monitor the movement and deformation of a small-scale fish cage deployed in currents, and results were compared with field measurements. 112 X. -H. Huang et al. / Aquacultural Engineering 74 (2016) 111–119