Two-Dimensional Numerical Modeling and Design Optimization of a Moored Buoy Under Ice Load

• Main Author: Cai, Ruolin (author)
• Other Authors: Hoving, Jeroen (mentor), van den Berg, Marnix (graduation committee), Delft University of Technology (degree granting institution)
• Format: Master Thesis
• Language: English
• Published: 2018
• Subjects: two-dimensional; mooring system; numerical modeling; buoy; Arctic; Lagrange
• Online Access: http://resolver.tudelft.nl/uuid:d8b1fc1d-c74c-4192-ba39-9a4b07d1899d

A single point mooring (SPM) system is one of the possible mooring systems in the field of Arctic floating production. It consists of a moored buoy to provide its anchoring unit with the capacity of mooring and ice sheltering. In the preliminary design phase, the performance of the mooring buoy must be assessed. This can be done by numerical modeling. This thesis provides a model for the two-dimensional numerical simulation of a moored buoy under ice loading, and it optimizes the buoy design based on the results of the numerical simulation. The model is constructed based on the discrete element method (DEM), where the elements consist of the elements describing the level ice, and one element describing the buoy. The numerical model is capable of simulating several ice-structure interaction mechanisms, including the ice compressive failure, the ice bending failure, and friction. The model consists of three parts. A compliant contact formulation describes the behavior of contacts between elements. Contact forces are solved implicitly using a Lagrange multiplier formulation. Lastly, the mooring system is described using the catenary equation. The model is validated against a number of analytical solutions, demonstrating that the model is capable of simulating the buoy-ice interaction. An example of the buoy design optimization process is demonstrated. The optimization aims to obtain a concept design of a satisfactorily performing moored buoy with minimized dimensions under a specific ice condition. Design criteria were determined for the maximum pitch angle and the maximum horizontal displacement of the buoy. Given the desired design criteria, one can obtain the most optimized buoy design after several phases of selection. Offshore and Dredging Engineering