The 12th International Conference on Hydrodynamics
18 – 23 september 2016, Egmond aan Zee, The Netherlands
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NUMERICAL STUDY OF A COUPLED WELL BOAT- FISH FARM SYSTEM IN WAVES AND CURRENT DURING LOADING OPERATIONS


Go-down ichd2016 Tracking Number 98

Presentation:
Session: Fluid structural inter-actions IV
Room: Room 4
Session start: 10:30 Tue 20 Sep 2016

Yugao Shen   yugao.shen@ntnu.no
Affifliation:

Marilena Greco   marilena.greco@ntnu.no
Affifliation:

Odd Faltinsen   odd.faltinsen@ntnu.no
Affifliation:


Topics: - Fluid-structural interactions and hydroelasticity

Abstract:

Dynamic response of a coupled well boat-fish farm system in waves and current is investigated numerically. The main purpose of the study is to determine how the presence and motions of the well boat will affect the behaviour 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 in extreme sea conditions. Before simulating the coupled system, some aspects related to the modelling of the well boat as well as the individual components of the fish farm system are presented. For the well boat, the equations of motions are solved in a coordinate system that coincide with the mean position of the well boat. Connection line forces as well as possible contact forces between the well boat and the fish farm system are duly considered. To avoid unnecessary complexity, we model a generic yet realistic fish farm system. The idealized fish farm system 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 [1],[2].The effect of the flow around the net cage and the transient responses of the well boat and the elastic floater are also accounted for. Then, the strategy to handle the coupling between different system components and the method used to estimate the contact force between the elastic floater and the well boat are explained. In particular, an intrinsic coupling strategy has been preferred to handle better strong coupling between different fish farm components while an iterative strategy is adopted for weaker coupling between the well boat and the fish farm. Intrinsic coupling means that the equation system is solved simultaneously. Numerical simulations for the coupled system in waves and current are performed to assess the robustness of the solution algorithm and to analyze the validity of the numerical predictions. Finally, a sensitivity analysis is performed to identify the most important parameters influencing the maximum mooring-line forces. The considered parameters include the distance between the well boat and the floater, the elasticity of the floater, the contact stiffness acting between the floater and the well boat, the pretension in the mooring lines and the mooring lines stiffness. REFERENCES [1] Kristiansen, T. and O. M. Faltinsen (2015). "Experimental and numerical study of an aquaculture net cage with floater in waves and current." Journal of Fluids and Structures 54: 1-26. [2] Endresen, P. C., et al. (2014). Simulation and Validation of a Numerical Model of a Full Aquaculture Net-Cage System. ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering, American Society of Mechanical Engineers.