MANOEUVRING MATHEMATICAL MODEL FOR A TWIN-PROPELLER TWIN-RUDDER SHIP

The MMG model is a modular type hydrodynamic model of proven value in various aspects of manoeuvring. However, this model was originally constructed for a single-propeller/single-rudder ship. In this paper, the various parameters included in the mathematical model for manoeuvring motion were investigated experimentally for a twin-propeller/twin-rudder ship. It was found that in general the MMG model, which was originally constructed for a single-propeller/single-rudder ship can be applied to a twin-propeller/twin-rudder ship, with the exception of the mathematical expression for the propeller wake. The authors modified the mathematical model for the propeller wake so that the corrected model can describe the characteristics for the propeller wake of a twin-propeller/twin-rudder ship. The predicted manoeuvring performance of a twin-propeller/twin-rudder ship was then compared with the results of free-sailing model tests showing the validity of the proposed mathematical model.