CFD approach to roll damping of ship with bilge keel with experimental validation

• CFD approach to the roll damping estimation of ships with bilge keel is presented.
• The estimates are validated with wave flume experiments.
• Damping without bilge keel is linear and that with it is strongly nonlinear.
• PIV experiments correlate the measured velocity field with that obtained by CFD.

The most common method of reducing roll motion of ship-shaped floating systems is the use of bilge keel which act as damping elements. The estimation of the damping introduced by bilge keel is still largely based on empirical methods. The present work adopts the CFD approach to the estimation of roll damping, both without and with bilge keel and validates the results with experiments conducted in a wave flume. Specifically, free oscillation tests are conducted at model scale to obtain roll damping, both by experiments and CFD simulation and reasonably good comparisons are obtained. The experiments also include PIV study of the flow field and attempt has been made to correlate the measured flow field with that obtained by CFD. The CFD methodology has the potential to determine rationally the size and orientation of bilge keels in design with reasonably accurate estimate of the additional roll damping that it provides to ship's roll motion.