Assessment of the Effectiveness of the Bilge Keel as an Anti-Roll Device in VLCC?Sized FPSOs

摘要

A Turret-moored FPSO under harsh conditions is supposed to alignwith wind-driven waves due to its weathervane capability. On the otherhand, the ship can find herself beam on to the seas in mildenvironments as a result of a combination of wind-driven waves andswell condition. This means that a misalignment between ship’sheading and waves can happen which leads to large amplitudes of rollmotion for a reasonably long time. This really gets worse in the case theFPSO is at low draft and the roll natural period is in the vicinity of thepeak period associated with the swell condition. It is well known thatone of the most effective devices to reduce the roll motion of ships isthe bilge keel. The importance of the bilge keel increasing the rolldamping moment stands out for resonant conditions. This paperpresents the results of free decay tests for various bilge keelarrangements as far as the roll damping coefficients are concerned. Inshort, tree representative drafts were considered for the FPSO and thebilge keel configuration varied from bare hull (no bilge keel) to bilgekeel 1.80m wide and 80% of ship’s length long. At last, a tailor-sizedbilge keel is defined for a typical F(P)SO operating at Campos Basin.