Fundamental Characteristics of Maneuvering Hydrodynamic Forces Acting on a Super-Slender Twin Hull Ship

Abstract

This report describes some problems concerning fundamental characteristics of maneuvering hydrodynamic forces acting on a super-slender twin hull ship advancing with steady drift angle. The contents consist of three parts. Interaction forces between two hulls, flow-direction behind the stern which is closely related to inflow-angle to a rudder, and forward speed effect on hydrodynamic derivatives in mono-hull condition are examined. By representing the ship by the center-plane distributions of normal doublets and sources, the hydrodynamic forces on the twin-hull ship and each of the hulls are calculated theoretically based on the linear lifting-surface theory. It is confirmed that calculated values obtained from the linear treatment agree well with the experimental results. Furthermore, assuming that the local wave effect can be practically neglected, a simplified calculation method for predicting the wave-making effect on hydrodynamic derivatives is developed. The present method gives an approximate estimation of the rate of increase of the linear derivatives due to the forward speed effect.