Assessment of a mathematical model for the manoeuvring motion of a twin-propeller twin-rudder ship

The MMG mathematical model [1] is well known and widely used for describing the manoeuvring motion of a ship. The MMG model is a modular type mathematical model which has proven to be useful in predicting various aspects of manoeuvring motion. However, this model was originally developed for the single-propeller single-rudder ship. Nowadays there are many multi-propeller multi-rudder ships, but little is known about the manoeuvring characteristics of the multi-propeller multi-rudder ship. In this paper, the authors develop the mathematical model to predict the manoeuvring motion of a twin-propeller twin-rudder ship, which was selected as one of the most popular configurations of multi-propeller multi-rudder ships. Initially, the various parameters included in the mathematical model for manoeuvring motion are investigated experimentally for a twin-propeller twin-rudder ship. The authors subsequently modified the mathematical model of the single-propeller single-rudder ship, and proposed a new mathematical model for the twin-propeller twin-rudder ship [2]. Finally, the predicted manoeuvring motion of the twin-propeller twin-rudder ship was compared with the test results of a free-sailing model in order to examine the validity of the proposed mathematical model.