ABSTRACT

This paper deals with coupled hydrodynamic analysis between gravity cage and well boat in operation. Dynamic behavior of the moored gravity cage under various current and wave conditions is first simulated, and the sensitivity of mooring line tension to added mass coefficient of the floating collar is studied. In the end, the effect of well boat is investigated on:

  1. hydrodynamic coefficient of the floating collar and,

  2. Froude Kriloff force on the floating collar in transmitted wave from the well boat. It is found that the maximum mooring line tension is not sensitive to the added mass coefficient of the floating collar in heave for frequencies smaller than 1.5rad/s. Considering the maximum mooring line tension, the effect of well boat on hydrodynamic coefficient of the floating collar can be neglected for frequencies smaller than 2.5rad/s. Froude Kriloff force on the floating collar in transmitted wave is much dependent on the wave length.

INTRODUCTION

The aquaculture industry is expanding due to the fact that wild fish stocks are reduced, while the world demanding of sea food is increasing. Traditional aquaculture, which has been in operation in near-shore or sheltered area, makes expansion difficult considering limited locations. Therefore, the feasibility of moving aquaculture into open sea is being studied. However, open ocean aquaculture calls for new technological challenges as fish farms are exposed to more severe waves, wind and current. On-going investigations on open ocean aquaculture cover many aspects, such as mooring system (Fredriksson et. al 2004), feeding system (Tsunoda et al. 2008), wave-current-net interaction (Lader & Fredheim 2001, 2006; Lader et al. 2007; Moe et al. 2010) and dynamic response of the floating collar (Fu & Moan 2012). However, according to the authors" best knowledge, the dynamic behavior of fish farming during the well boat operation, say harvesting, has seldom been touched upon, even for aquaculture in sheltered area.

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