An experimental and numerical study of roll motions for a barge-type LNG FPSO

Abstract

In the estimation of roll responses for a barge-type LNG FPSO, the evaluation of correct nonlinear roll damping is critical. The box-type section of FPSO causes a fair amount of viscous damping effect. Free roll decay tests is conducted to estimate nonlinear roll damping for a barge-type LNG FPSO of three different loading conditions. The roll motion RAO is deduced by model tests in the wave condition of wide banded spectrum. In numerical calculation, the quadratic damping is considered as equivalent linear damping. Tested roll performance in JONSWAP wave spectrum is compared with numerical result. These two results show good agreement, in spite of proximity in peak wave period and roll natural period. Copyright ？ 2004 by The International Society of Offshore and Polar Engineers.