NUMERICAL STUDY OF A COUPLED WELL BOAT-FISH FARM SYSTEM IN WAVES AND CURRENT DURING LOADING OPERATIONS

Dynamic response of a coupled well boat-fish farm system in waves and current is investigated numerically. The main purpose is to determine how the presence and motions of the well boat will affect the behavior of the different components of the fish farm. In particular, we focus on the influence on the maximum forces in the mooring lines during loading operations. To avoid unnecessary complexity, we model a generic yet realistic fish farm system. This consists of an elastic floater, a flexible-circular-bottomless net cage, sink weights and a realistic mooring system. The various components are modelled according to state-of-the-art theoretical and numerical formulations. Connection line forces as well as contact forces between the well boat and the fish farm are duly considered. For the contact forces, both a direct method and a penalty method are examined. A systematic variation of the environmental conditions made by current, waves, and combinations of them, is carried out. Numerical results show that the mean steady state mooring loads for the coupled system will increase significantly compared with those for the fish-farm system alone due to the nonlinear viscous current loads and mean drift forces on the boat. The presence of the boat will also exert an important influence on the deformation of the floater and may threaten the structure integrity of the fish farm even in moderate sea states.