Deepwater Platform Mooring Systemanalysis And Visual Simulation

With the development of composite materials science, automatic controltechnology and information technology, marine engineering equipment has ainclination towards deepwater fields. In order to study the performance of mooringsystem in deep water, this dissertation focuses on the research of a sixth-generationdeepwater semi-submersible drilling platform. Based on the three dimensionalpotential flow theory, hydrodynamic analysis on the deepwater semi-submersibleplatform is performed by using the software AQWA-LINE. Firstly, thehydrodynamic coefficients in regular waves is calculated, including the added massmatrix, damping coefficients matrix, response amplitude operators (RAOs), etc..Thefirst-order fluid forces acting on the platform are calculated by integrating thehydrostatic pressure over the wetted surface of the platform. The mean second-orderwave drift forces are calculated by using a far-field solution. The results show thatthe magnitudes of the first-order fluid forces have reached107, while thesecond-order drift forces are2to3orders lower to the first one.The preliminary design of the mooring system is carried out by using thesoftware AQWA-LIBRIUM, which analyze the platform based on the hydrodynamicdatabase established by the AQWA-LINE software. Taking the working conditions inrelevant sea areas into consideration, the feasibility of different kinds of mooringlines is checked according to the requirements specified in the design manual. In theend, the composite mooring lines composed of anchor chain, polyester fiber cableand wire rope are chosen. The mooring lines symmetrically lay out around theplatform and all of them are taut. The equilibrium positions of the platform indifferent-direction wind and random waves are calculated in the frequency domainas the basis for the time-domain analysis.In order to obtain the extreme responses of the platform and the mooring lines,the duration curve of the displacement of the platform and the tension in the mooringlines are calculated by using the AQWA-DRIFT software. The results show that theheave of the platform is within4.5meters, and the horizontal displacement is lessthan6%of the depth in self-preservation condition, which means the design meet the requirements.The entity model is established by Creator modeling software, and in order tosimulate the movement of the objects in this system, dynamic model is also built.The simulation function is realized by API functions in the Vega software package,using VC++development platform. The OpenGL technology is combined with VegaAPI functions to solve complicated problems in the chain form. Relevant data areextracted from the results which AQWA software calculates and the displacement ofthe mooring line is fitted by using Bezier curve and parabola.