Influence of initial disturbances on ship stopping performance by propeller reverse rotation

The stopping performance of ships is important to avoid collisions at sea during an emergency. To ensure sufficient stopping performance, stopping tests were performed in a full-scale trial. However, it has been pointed out that initial disturbances, such as slight ship motions represented by heading deviation, hull lateral velocity, and yaw rate, which occur immediately after the start of the stopping test, have a significant influence on the stopping performance by the propeller reverse rotation. In this study, we investigate the influence of a slight initial disturbance on the stopping performance by tank tests and stopping simulations, and discuss the standard for acceptable initial disturbances in the stopping test. The results show that the track reach ( R_T ) index is less susceptible to initial disturbances than the side reach and head reach indices. The influence of the initial disturbance on R_T is closely related to the course stability of the ship. In the ballast load condition with excellent course stability, the influence of the initial disturbance on R_T is small. In contrast, in the full load condition with poor course stability, the influence of the initial disturbance is large, resulting in more variations of R_T . Based on the simulation results, a standard for acceptable initial disturbances is presented for a bulk carrier.