Rudder effectiveness correction for scale model ship testing

The authors propose an idea of rudder effectiveness correction for free-running manoeuvring tests using scale models. The idea aims to realize the full-scale-equivalent manoeuvring motion with scale models using the auxiliary thruster that the authors developed. The auxiliary thruster can generate time varying forward force needed for the rudder effectiveness correction. The auxiliary thrust is represented by the force required for the skin friction correction multiplied by the newly defined rudder effectiveness correction factor. The propulsive performance of the model and full-scale ships in steady straight running determines a value of the factor. Theoretical calculations using the modular mathematical model applied to a container ship and a tanker clarify characteristics of the factor. The tank tests and numerical simulations confirm the feasibility of the idea.