Steel Lazy Wave Riser(SLWR)와 계류된 부유체의 연성응답에 관한 수치해석 연구

Abstract

A numerical study was performed on the coupled responses of steel lazy wave riser(SLWR) and moored floating body. Prior to the coupled analysis, the floating body motion was evaluated with the frequency domain and time domain. Wave exciting force, drift force, wave damping and the added mass of the FPSO were calculated for the coupled analysis. Roll damping ratio was selected to 4% of critical damping. Spread mooring system was considered for the positioning of the FPSO andriser system. This mooring system consists of chain-polyester-chain with 4 by 4 mooring lines for 1,600m of water depth. They satisfied the safety factors of mooring line tension and offset criteria for intact and damaged conditions. The steel lazy wave riser was selected in this study. The inner diameter of the steel pipe is 9 inch. Riser wall thickness was selected according to API guidelines considering well pressure. The riser configuration was designed considering effective tension, clearance at sag/hog position, bending moment and the hang-off angle at the critical region etc. The comparison was performed between the coupled and the uncoupled models. The coupled model included the wave exciting force, wave drift force, added mass and damping. The uncoupled model considered the vessel motion with displacement RAO of 1st wave motion. The vessel motion and the mooring tension were compared according to coupled effects. There is no effect on th