Research On The Design And Hydrodynamic Performance Of The Mooring System Of The Nearshore Permanent Mooring Platform

Represented by the "Academician Lomonosov" floating nuclear power platform,the permanent berthing requirements of special offshore platforms put forward extremely high requirements on the comprehensive performance of its mooring system,including: harsh environmental conditions,long structural life,high reliability,quick release,adapt to tide level changes,etc.The existing mooring system form cannot meet the above requirements.Therefor this paper designs a string mooring system with strong structure,modular design,omnidirectional restoring force,simple interface and adjustable balance position to solve the above problems.Because the new mooring system is different from the traditional cable structure and the working principle of the existing mooring system is quite different,there is no relevant experimental data to support its performance analysis,there is a lack of clear qualitative understanding of the influence of the system’s own design parameters and environmental parameters,and there is a lack of mature mathematical model tools as the research and design basis.Therefore,based on the three-dimensional potential flow theory,this paper establishes the numerical model of the wharf berthing platform by using the boundary element method,and qualitatively analyzes the hydrodynamic performance of the platform applying the mooring system through numerical simulation,so as to verify its adaptability to the permanent berthing demand.Firstly,according to the structural characteristics of the new type of String-type mooring system,the principle of providing the restoring force and the demand of wharf tide level adaptability,this paper puts forward the design method and principle of the adaptive system and the factors that should be considered in the design,so as to facilitate the follow-up research and model design in engineering practice.Then,based on Aqwa software,the numerical models of platform berthing,String-type mooring system and traditional wharf mooring system are established.The hydrodynamic performance and motion response of the platform with two mooring systems under the combined action of regular waves with different tide levels,different frequency amplitudes and wind waves close to the actual extreme environmental conditions are calculated respectively.Through the analysis of the simulation results,it is found that the rolling,swaying and heave motions of the mooring platform are the most severe under the action of transverse waves in the wharf area,but the heave motion is less affected by the mooring form,so the rolling and swaying motions of the platform need to be paid attention to;The mooring platform is obviously affected by the change of the tide level of the wharf,and the platform is more dangerous when the tide level of the wharf is the highest;However,compared with the cable mooring platform,the motion range of the String-type mooring platform is balanced,stable and controllable at each tide level,which proves that it has good adaptability to the change of wharf tide level.By providing omni-directional restoring force,the mid chord mooring system strengthens the restriction of the platform rotation motion,greatly weakens the most severe rolling motion of the mooring platform,transfers the energy of environmental load to translational motion,and further strengthens the restriction of the overall motion of the platform.To sum up,this paper verifies that the String-type mooring system is more suitable for the permanent berthing of special offshore platforms than the traditional mooring system.