Roll characteristics contributed by a bilge keel using a high-order fractional step finite volume solver

Abstract

This paper follows the previous work [Ocean Eng 199: 1–15] to study roll characteristics contributed by a bilge keel through investigating the differences between roll characteristics of the naked mid-section of a KVLCC2 and the ones of the hull fitted with a bilge keel. Harmonic excited rolls are simulated by a high-order fractional step finite volume solver. Roll moment, roll damping, added mass moment of inertia, hull pressure are explored. Besides, two damping components of a bilge keel, due to the force normal to the bilge keel and the additional pressure on the hull induced by the bilge keel, are studied. Five parameters, namely roll amplitude, roll frequency, ship draught, height and thickness of the bilge keel, are concerned. In results, the additional roll moment due to the bilge keel exhibits a strong nonlinearity. The two components contribute to the additional roll moment quite the same amount, whereas wave radiation contributes little and negligible. Added mass moment of inertia is saturated when roll amplitude becomes large. Hull pressure induced by the bilge keel is normally positive at the front of bilge keel and negative at the back side and attains maximum approximately right at the base of the bilge keel.