Study On Hydrodynamic Performance And Mooring System Of Semi-submersible Platform

Exploration and exploitation of marine energy and mineral resources has promoted the flourish development of Marine Engineering,and semi-submersible platform has become one of the mainstreaming tools in exploring and developing marine resources because of its strong ability to resist wind and waves,to adapt to a wide range of water depth and large load.Therefore,analysis of the hydrodynamic performance of semi-submersible platform,calculation of motion state under the combined action of wind,wave and currency as well as the tension response of the mooring system are of great importance.This paper studies the hydrodynamic performance and mooring system performance of a semi-submersible platform which operating in 300 m water depth of South China Sea,On this basis the influence factors of the semi-submersible platform motion response are discussed.The main work of this paper can be concluded as follows:Firstly,based on the three-dimensional potential flow theory and the investigation of the development and research status of the semi-submersible platform at home and abroad,the hydrodynamic model of semi-submersible platform is built by ANSYS-AQWA software.The hydrodynamic performance of platform is calculated and the hydrodynamic parameters such as added mass,damping coefficient,amplitude of motion response and wave force are obtained.Secondly,according to the water depth and the characteristics of semi-submersible platform,the mooring system of the platform is initially designed as a symmetrically catenary mooring system with 8 anchor chains.Then using the result of frequency domain analyses in the previous chapter,and do coupled dynamic analysis of the semi-submersible platform and mooring system under the conditions of survival and operation with wind,current and waves.The response time curve of the platform and the tension curve of the mooring line are calculated.Thirdly,in the frequency domain and time domain calculation,a typical working condition is selected and the simulation results are verified and analyzed by the model test results.The results show that the simulation results in the regular wave are in good agreement with the model test results.In the complex time domain analysis,although there is some error between the two methods,the simulation method still can accurately predict the motion response and mooring performance of the platform.Therefore it is reliable and practical to use AQWA software to calculate the hydrodynamic performance of the platform.Finally,on the base of above-mentioned researches,the influence factors of platform's motion response are discussed by numerical calculation.The calculation model is still the original semi-submersible platform,and calculated the change regulations of platform's motion response with different height of gravity center,draft and heave plate set.It can provide some reference for the optimization of the motion response of the semi-submersible platform in the future.The content in this paper can be referential to investigate the hydrodynamic problems of semi-submersible platform by using AQWA software and model test;at the same time,the results obtained from the study of the influence factors of the motion response have some significance for the design and structural optimization of the semi-submersible platform.