Sensitivity Analysis of Different Parameters of Taut Mooring System of a Truss Spar

The taut mooring system is widely used for some advantages, such as smaller mooring radius, lighter total weight and better anti-corrosion performance. In this paper, the taut mooring system of a Truss Spar platform which was taken as the research object was investigated under the condition of 2000 m water depth in South China Sea. Firstly, the main body of the platform was analyzed in frequency domain based on the 3-d potential theory, and then the nonlinear solutions of platform displacement and mooring line force were obtained by using coupling analysis method in time domain, which determined the preliminary design parameters of mooring system. The sensitivity of the taut system is studied by changing several design parameters such as the top angle of mooring line, cable hole position and method of mooring disposal. In summary, the variation of the motion and dynamic response of the platform and mooring system has been explored and summarized by studying the design process and influential parameter of dynamic characteristics of mooring system and optimizing ideas of relevant parameters, which can further provide technical support and engineering reference for the design and application of the taut mooring system of deepwater Truss Spar platforms.

Effects of Water Inside Semiclosed Moon Pool on the Hydrodynamic Coefficients and Heaving Damping of a Truss Spar Platform

The hydrodynamic coefficients and heaving damping of a truss spar platform were studied by the computational fluid dynamics (CFD) method with considering the semiclosed moon pool. A partial model was established to investigate the added mass and viscous damping of platform heaving; a full model and a simplified model were established to study the nonlinear damping of platform heaving. The influences of opening ratios of moon pool on the added mass and viscous damping of platform heaving were analyzed. It is found that the natural period and the heaving added mass of the platform increase if the semiclosed moon pool is considered. Different opening ratios of the moon pool will lead to different heaving damping of the platform and dynamic pressure acting on the guide plate of the moon pool. In practice, an optimal opening ratio of the moon pool can be designed. The numerical results were verified by comparing with the results of model experiments.

Nonlinear Analysis of Stochastic Heave Motion for Truss Spar

Applying the Path Integral Solution Method, the stochastic heave motion of Truss Spar platform was studied in this paper. Taking a platform for example, probability density function of stochastic heave motion amplitude was calculated under the conditions of different wave excitations. The results show that, the changing process of probability density function in the time domain has an obvious periodicity. As the increasing of external excitation, the heave motion amplitude and speed both increases. Meanwhile, as the increasing of excitation amplitude, the probability density function of heave motion has a more pronounced periodicity.

Stochastic Analysis to Truss Spar Platform in Deep Sea

Truss spar model was tested using regular waves in a wave basin and the responses in surge, heave and pitch were measured. A program was developed to determine the responses using numerical method. This program was run using the model parameters. The results are agreed well with the corresponding results obtained from the test measurements. Then this program was applied to a prototype spar simulated results were compared with the corresponding numerical results and test measurements.