A Study on Motions and Drift Forces of a Multibody Floating System in Waves

Abstract

In this paper, the application of three dimensional source technique for computations of motion responses and drift forces for multi-body floating system with zero forward speed in waves are investigated. The mean wave drift forces are obtained by far field and near field (direct pressure integration) methods. Numerical results for the first order motion responses and the mean wave drift forces for a parallel arrangement of a FPSO (Floating Production Storage and Offloading Unit) and a LNG carrier are discussed. Some comparisons are made for a single floating body (semi-submersible) as well as for a simple multi-body system of a cylindrical body with a box shaped hull. Numerical results for motion responses are compared with experimental ones for the FPSO-LNG system and also results for mean wave drift forces obtained from both of the methods are compared with experimental ones. The trend of the results as well as correlation between both of the methods found to be comparatively well in agreement. The effects of roll damping to the second order wave drift forces for sway and yaw are also discussed. 1.