Free Roll Decay of FPSO and FLNG Hulls With Bilge Keels Through Experimental Tests and CFD Simulations

The objective of present paper is to assess the roll damping characteristics of FLNGs and FPSOs. The roll damping characteristics are examined through the three prediction methods; 1) Ikeda’s empirical method, 2) experimental tests and 3) CFD simulations. Practically, design variables that can be adjusted to reduce the roll motion include only the bilge radius and the height of bilge keel. In the present paper, a parametric study has been made considering various combinations of bilge radius and bilge keel height.

The three prediction methods constantly show that the roll damping of FLNG and FPSO hulls considered in the present paper increases with increasing bilge keel height and decreasing bilge radius. Using experimental and simulation data with systematic variation of bilge radius and bilge keel height, it is shown that the roll damping can be correlated with a function b_bk/b_{bk_max}^0.8. Using this relationship, a design guideline is proposed to simultaneously optimize the roll damping performance, the structural integrity of bilge design and the constructability related to bilge design of the hull form of FPSOs and FLNGs.