Bank interaction effects on ships in 6 DOF

Abstract

This paper presents the used mathematical formulations to predict ship bank interaction in six degrees of freedom (6 DOF) as applicable in a ship manoeuvring simulator. The mathematical models are based on a comprehensive database (+10,000 model tests carried out in a towing tank) and are capable to cope with a variety of realistic cross sections, based on a limited set of coefficients. Compared to previous publications on bank effects, the lateral force of these bank effects with point of application at the forward perpendicular, is now predicted with an alternative mathematical model that offers the same predictability as the original one, but that better describes the physical background. Moreover, new formulations are included to predict the bank induced components of the ship in the vertical plane (heel, midship sinkage and trim). Although these tend to be neglected, the experimental results show that the effect of confinement and eccentricity can be significant and that a 6 DOF mathematical model is needed for a correct prediction of the manoeuvring behaviour.A difficulty that is still present is the correct separation of the open water contribution and the contribution due to confinement. This is especially the case for rather high displacement ship models, such as the KVLCC2 tanker, in the 7 m wide towing tank, that even sense the tank walls when being towed on the centreline. This topic will be coped with in future publications, along with an extension for ships that sail with a drift angle.