Turning of a Heeled Ship

抄録

If an unexpected load collapse occurs, a ship may heel. The ship must navigate safely in the heeled condition until the destination port is reached. In this paper, the turning performance of a heeled ship is investigated. Firstly, a free-running test is conducted using a pure car carrier model to capture the turning characteristics with a rudder angle ±35° of the heeled ship. In starboard turning of a ship with port side heel, the turning radius decreases with an increase in the absolute value of the initial heel angle (φ₀). In comparison, there is no significant difference in the port turning trajectory. The effect of the initial heel angle on the turning performance differs, depending on the port and starboard. We then propose the maneuvering simulation method for the heeled ship. To confirm the validity of the proposed method, the turning simulation results were compared with the free-running model test results. The simulation results are roughly in agreement with the model test results, although the simulation accuracy deteriorates in the case of large heel angles, such as φ₀=±20°. Based on the linear theory for maneuverability of the heeled ship (Yasukawa and Hirata, 2013), the heel effects on the turning performance are discussed and summarized as follows: a turning motion appears due to the effect of the heel-induced lateral force and yaw moment which are in proportion to the magnitude of the heel angle, and the course instability increases with the heel angle. Both effects can explain the turning behavior of a heeled ship that is observed in free-running tests.