| The main purpose of this thesis is to predict the motions of a Spar platform due to wind, current and wave. And then, an investigation on three methods of computing current force is conducted. Besides, some comparisons among several methods of calculating hydrodynamic forces of hard tank are performed.The wave loads of the whole Spar are evaluated by Full Slender Formulation. Especially, it is applied for the truss structures, which is the extension of the Full Slender Formulation. The wind pressure is calculated as the rule of API, and the wind velocity is varied with height. The current velocity is a constant, and it is considered by superposition of water particle velocity. The Spar platform is treated as a rigid body; the nonlinear equations of motions are adopted by this study. At last, a code is developed by extending the code for Classic Spar with three freedoms motions from Q.W.Ma&M.H.Patel, and it can give the prediction of Spar motions with six degree freedoms under waves, currents, winds and mooring loads.This thesis performs some predictions and analyses by a Classic Spar and a Truss Spar, the main contents and results are as following:(1) Comparing the results of this work to those of experiments, and satisfactory agreement is achieved. Besides the motions results from special wave and current direction of this code are checked by theory analyses. From above, the reliability of the numerical program can be proved.(2) Predicting Classic Spar motions with six degree freedoms due to directional wave, current, wind, and mooring system.(3) Computing the wave loads of the whole Classic Spar by three methods, their results reveals significant differences with the different wave periods.(4) Predicting Truss Spar motions with six degree freedoms due to directional wave, current, wind and mooring system.(5) Investigating on three methods for calculating current loads is conducted by a Classic Spar and a Truss Spar, and the remarkable results are demonstrated. |
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