| Abstract | The present work examines the loads on moored/DP-assisted drillships and their responses in managed pack ice. Numerical simulations are used to determine deformations and stresses within the ice cover and the movements of the vessel. The results give ice forces and moments on the vessel, as well as its surge, sway and yaw responses. The drillship assumed in this simulation work has a length of 230 m, a beam of 42 m, and a mass of 100,000 Mt. Simulations examine a case representing a moored vessel in a managed ice field consisting of 50 m floes that are 1 m in thickness, moving at a constant speed of 0.3 m/s. For ice moving along the surge direction, the peak surge force was approximately 2 MN. The corresponding maximum surge was 1.5 m. A parametric study further examines several aspects of ice interaction with the vessel. The results quantify various effects of ice management (the role of floe size), ice thickness and drift speed, the direction of ice movement, and stiffness of the mooring system. A case of combined mooring and thruster-assisted mooring is also examined. The additional contribution of the thrusters (or control of the DP system) is shown to somewhat reduce the offsets of the vessel. The work presents a methodology for evaluating the stationkeeping performance of vessels in managed pack ice and quantifying the role of the mooring/DP system characteristics. |
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