横傾斜状態で航行する船の流体力微係数と操縦性

Abstract

Oblique towing test and circular motion test with changing heel angle were carried out to capture the hydrodynamic forces acting on ship models of container ship, pure car carrier and ferry. Based on the measured forces, the hydrodynamic derivatives with respect to lateral velocity (υ), yaw rate (γ) and heel angle (φ) were obtained for surge force, lateral force, yawing moment and roll moment. Using the derivatives obtained, ship maneuverability traveling in heeled condition was discussed based on a linear theory presented in this paper. As a result, the authors made clear the maneuvering characteristics of heeled ships. When the ship travels in heeled condition to starboard side, she turns to port side. Such characteristic depends on the order of magnitude and the plus (minus) sign of the hydrodynamic derivatives with respect to heel angle, Y' φ and N' φ. In case of the ferry, the turning strength per unit heel angle was about 1/3 comparing with that per unit rudder angle.There is a trend that the turning performance improves with increasing the heel angle. This is due to the course instability appears with increasing the heel angle. The course stability is deeply related to nonlinear derivatives with respect to heel angle, such as Y' υφφ, Y' γφφ, N' υφφ and N' γφφ.