Abstract: Based on computational fluid dynamic theories，the simulations of roll decay and forced roll motion of a three dimensional rectangle floating production storage offloading, a new concept ocean floating structure, were carried out by using overset mesh technology and solving Reynolds Averaged Navier-Stokes equations with the consideration of free surface effect. In addition, the scale factor and gird study verification were considered. Energy method was adopted to compute the roll decay damping coefficients. To verify the methods, a roll decay motion was predicted for a surface combatant. The results show a good agreement with the experimental data. And then a series of prescribed roll motions on various amplitudes and frequencies of different modifications to origin design were executed due to its lack of roll stability.

Key words: floating production storage offloading (FPSO), free-roll decay, forced roll, roll damping simulation