Abstract: Abstract： The model of an infinite long cylinder submerged in fluid, which vibrates vertically, was investigated in this paper. Based on the analysis of incompressible flow field in limited area, the influence of fluidwidth, fluiddepth and submerge enceratioon added mass was analyzed using numerical computation. Thus, based on Lewis’ method, a fast prediction formula for added mass of underwater vehicle was proposed. The results show that the rigid wall leads to an increase in added mass, but as the distance increases (usually 5 times the crosssectional radius), the effect of the wall can be neglected. However, the free surface may reduce the added mass, and the effect can be ignored when the distance between the cylinder and the free surface is up to 6 times the crosssectional radius. The velocity potential on the free surface can be considered as zero only when the cylinder is vibrating at a high frequency or is far away from the free surface.

Key words: Key words： added mass, ship vibration, Lewis’ method, fast prediction