Numerical Analysis Of Interaction Of Floating Structuresand Mooring Systems

As exploitation of offshore oil and gas resources goes from shallow todeep water, floating structures play a more and more important role asequipment for offshore engineering. Investigating the interaction of floatingstructures and mooring systems can lay the foundation for researches onmotion response performance of floating structures in waves and thereforeprovide reference for the design of floating structures.With CFD as its technological means and the open source toolboxOpenFOAM as the platform, and based on the CFD solver called naoe-FOAM-SJTU which is designed for naval architecture and oceanengineering,a mooring systemmodulenamednaoeFOAM-ms is developed,extending the ability of the solver to deal with hydrodynamic problems offloating structures. This module can solve mooring systems using eitherstatic or dynamic analysis methods to meet various requirements inengineering. Integration of the module establishes the link between mooringsystems and floating structures, and provides a way to analyze theinteraction. Owing to its inherent extensibility, more solving methods couldbe added easily in subsequent development. The application is verifiedthrough comparison with other numerical and experimental tests. By takinga2D floating breakwater and a deep-water semi-submersible drillingplatform as examples, naoe-FOAM-SJTU is used to obtain motion responseof the structures, while static and dynamic analysis methods are appliedseparately to solve the mooring systems. Satisfactory results are obtained,showing that naoe-FOAM-SJTU is capable to handle motion responseproblems of floating structures in waves. On the basis, by changing mooring system parameters through threeways, i.e., different analysis methods, different length ratio of mooring linematerial and different mooring system arrangement for the angle betweenlines in the same group, naoe-FOAM-SJTU is utilized to solve motionresponse for the same semi-submersible platform in waves. Differencesbetween responses are inspected and used to evaluate the influence of thechange of mooring system parameters on the motion responses. The resultsshow that the degree of influence of the change of mooring systemparameters varies from the motion response for different degree of freedom.The influence to surge motion is relatively more notable. Performance ofmotion response of this degree of freedom can be improved by choosingsuitable parameters of mooring systems.