Analysis Of Random Motion Of Deepwater Semi-submersible Support Platforms Under The Action Of Wind And Wave Loads

In today's social situation,the exploration and exploitation capabilities of deep sea oil and gas resources have become an important manifestation of the country's comprehensive strength.As an important tool to support mining work,the deepwater semi-submersible support platform has gradually become the focus of researchers in various countries.When studying the hydrodynamic performance of the platform,how to accurately calculate the wave load becomes the first problem to be solved.The calculation methods of wave loads have been relatively mature at present,mainly including Morison equation method and three-dimensional potential flow theory.In addition to the wave load,the platform will also be subjected to random wind loads under actual conditions.Therefore,it is of great practical significance to analyze the motion response of deepwater semisubmersible support platform under the combined action of random wind and waves.In the general analysis process,random wind and wave actions are often simulated independently,and the coherence effect between them is usually not considered,which makes it difficult to ensure the accuracy of the calculation results of platform motion response,and even serious underestimation will occur,which brings huge potential safety hazards.Based on the above problems,the following research work is carried out in this paper to analyze the random motion response of deep water semisubmersible support platform considering the coherence between wind and wave:1)The wave load calculation method based on Morison equation is analyzed,and the sway response of a jack-up platform under random wave excitation is numerically calculated;2)The method of establishing the finite element model of deepwater semi-submersible support platform by using SeSam software is studied,and the coupled time domain analysis model between platform and mooring system is established;3)Based on the fluctuating wind speed spectrum,wave spectrum and the coherent function model of fluctuating wind and wave determined by the measured data,the calculation methods of wind load and wave load are proposed;4)By using the established method,the random motion response of a 1500 m deepwater semi-submersible support platform is analyzed,and the prediction of the platform motion is carried out based on the analysis results.Based on the SeSam software,the influence of wind-wave coherence on the motion response of the platform is analyzed by manually inputting wind load and wave time history.The results show that when considering the coherence between wind and wave,the motion response of each mode of the platform increases slightly compared with that without considering the coherence.The research in this paper has certain theoretical and practical value in predicting the motion response of deepwater semi-submersible support platform under random wind and wave loads.