| In order to solve the long-term dependence of oil and gas resources on foreign countries,China has formulated a series of relevant policies in the 14-th Five-Year Plan to vigorously develop offshore energy and equipment.As an important equipment for the development of offshore oil and gas resources,offshore platforms had attracted more and more attention.In the past,offshore platforms were mostly operated independently.However,with the continuous development of ocean towards deep and open sea,the demand for operation modules has increased.The function of a single offshore platform has gradually failed to meet the requirements,it will also lead to the deterioration of the operation and living environment of the operators,affecting the production efficiency.In this regard,some scholars have proposed to combine two or more offshore platforms into a joint operation,and connect the offshore platforms with different functional modules through the mooring system.It makes the function of a single platform specialized and realizes complementary advantages to meet the different needs of marine development.In this thesis,a marine energy station and a typical semi-submersible platform are taken as the research objects.The wave slamming of the dual-platform joint operation is studied and analyzed by numerical simulation and model experiment.The research content is an important part of the National Natural Science Foundation ’Design method of double platform new hybrid mooring system and multi-body coupling hydrodynamic analysis’.The specific research contents include:(1)The hydrodynamic characteristics of dual-platform joint operation were analyzed.Firstly,the two platforms are modeled and meshed,and a mooring system was designed for the joint operation of the two platforms.Then,the potential flow theory is used to study the characteristics of hydrodynamic parameters such as radiation damping and added mass,RAOs and first-order wave force under the coupling of the two platforms in the frequency domain.Finally,the environmental conditions are designed according to the characteristics of the joint operation area of the two platforms,and the focus points of wave slamming characteristics are obtained according to the influence of wave slamming.(2)The physical basin experiment of the dual-platform joint operation was carried out to verify the accuracy of the numerical model and the feasibility of the simulation method.According to the similarity criterion,combined with the actual size of the experiment basin and the capacity of wave maker,designed 1: 100 scale dual-platform model and mooring system.The dual-platform joint operation experiment under regular wave conditions was carried out in the basin.The accuracy of the numerical model and the feasibility of the numerical simulation method were verified by comparing and analyzing the attenuation experiment,the motion response of the platform and the wave slamming results.(3)Based on the modified and verified numerical model,a time-domain fully coupled analysis method is established to analyze the wave slamming load characteristics of dualplatform joint operation under working conditions.And studied the sensitivity of wave direction angle,wave height and period by using this analysis method.The results show that the slamming load changes in the horizontal and vertical directions are not obvious on the same brace.On the same column,in the range of wave slamming,the higher the position with the greater the slamming load,but the fewer the times of slamming.On the same platform,the column with the greater slamming load when near the other platform due to the coupling effect.The change of wave direction angle has obvious effect on the slamming load of the horizontal direction of the brace and the columns,and has little effect on the slamming load of the vertical direction of the brace.The change of period has little effect on the slamming load of the platforms.The change of wave height is positively correlated with the slamming load of the platforms.(4)Based on the time-domain fully coupled analysis method,the wave slamming load characteristics of dual-platform joint operation under freak wave conditions are analyzed.Through the focused wave model,the strong nonlinear freak wave is realized at a specified time.The wave slamming characteristics of the dual-platform joint operation under the ‘New Year Wave’,the sensitivity of freak wave height and wave period parameters are analyzed.The results show that the platforms will be strongly slammed by waves and accompanied by large negative pressure when freak waves occurred.The slamming load on the measuring point increases with the increase of wave height and decreases with the increase of wave period.In summary,this thesis conducts a more in-depth study on the slamming load distribution characteristics of the key parts of the dual-platform joint operation under working conditions and freak wave conditions through the time-domain fully coupled analysis method.The research results have certain guidance and reference value for the design and engineering application of dual platform joint operation. |
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