Investigation On A Dock Mooring FSRU

With the advance of socialist modernization construction,China’s economic development has entered a new normal,and environment carrying capacity is close to the limit,so we must conform to people’s expectations of green water and blue sky,pay attention to ecology environment,and format the concept of low-carbon and circular economy.Natural gas,as a kind of clean energy with high safety and high heat,has a great effect on the realization of socio-economic sustainable development and the construction of a good ecological and energy structure.FSRU(Floating Storage and Re-gasification Unit),the most widely used offshore floating LNG receiving terminal,will be more and more widely used for power plants and ordinary urban users.When FSRU is moored to wharf separately or LNG is unloading nearby,the operation and safety state of the system depends on mooring line tension,cushion pressure and 6-DOF motion.Therefore,it plays an important role in the design work of FSRU that investigate on the hydrodynamic performance of wharf mooring FSRU in adverse conditions.A being designed FSRU is chosen in this paper to analysis the ship motions,mooring force and cushions stress under the marine environment where the wharf is,using both the classical potential flow calculation and model test method.According to the classical potential flow theory,the hydrodynamic analysis of FSRU in the frequency domain is conducted,in the loading condition of no-load,10%,30%,50%,70%,and full-load.The results showes that: the trend and shaoe of RAOs are roughly the same,but amplitude differences exist among part of the curves.By using the frequency domain calculation results,the mooring coupled analysis of FSRU is carried out in time domain,to botain time history of mooring line tension,cushion pressure and 6-DOF motion under different loading conditions.The results show that: the maximum force of mooring line and cushion in beam sea is greater than that of other different angles,and the maximum force of mooring line and cushion of 30% loading condition is greater than that of other loading conditions.Further,the numerical analysis multi-body numerical model of FSRU-LNGC is established,and the hydrodynamic performance of the system is analyzed,and the dynamic response of the mooring system is obtained.The calculation results show that: the increase of FSRU loading and reduce of LNGC loading FSRU has opposite effect on the variation trend of moving maximum amplitude for FSRU and LNGC.In order to verify the reliability of numerical results,corresponding model tests are designed depending on the extreme marine environmental conditions once in a year,and the experimental results are compared with numerical simulation results.Model tests includes decay tests in static water,white noise irregular wave tests and irregular wave tests including wind and current.Comparing experimental results with numerical results,the conclusions are as follows: numerical method preforms well on the prediction of the motion and mooring forces of FSRU moored alone and the result can be used as design basis.By doing that,amendments should be made to increase the data 10%.However,the result of numerical methods for FSRU moored on a dock with LNGC side by side is not so good,so it can only be used as reference rather than design basis.In summary,this paper has carried out systematic research on the FSRU wharf mooring system,and got the key conclusions,and put forward feasible suggestions to improve the engineering practice.It has a certain guiding significance for the design and improvement of FSRU and its mooring system.