Vortex shedding and roll damping for hulls with rounded bilges

Vortex shedding and eddy generation can provide a substantial contribution to the hydrodynamic roll damping of vessels. While sharp-edge bilge geometries generally result in greater damping, a more rounded bilge may be beneficial for the other ship motions and mooring design. To this end, the effect of the bilge rounding on the vortex shedding dynamics and the hydrodynamic damping of hulls is investigated numerically. A series of new computations of the response of hulls with differing bilge radii and subject to forced oscillatory motion are reported. The severity of the vortex shedding and the magnitude of the damping is shown to depend strongly on the bilge geometry. Computations using an efficient isolated edge discrete vortex model are also found to be generally in qualitative agreement with the CFD results. The results extend the relatively scarce literature on the effect of bilge rounding and can assist in informing hull design and concept selection.