Equivalent Simple Mathematical Model for the Manoeuvrability of Twin-propeller Ships under the same propeller-rps

Twin-propeller ships are widely used for from high-speed coastguard ships to low-speed wide beam cargo ships. One of the authors1) firstly proposed the simulation method for twin propeller and twin rudder ships by means of applying MMG’s mathematical model. After then, some experimental researches2)～4) have been done. However, the manoeuvring prediction for these ships is not easy because propeller and rudder forces are different between port and starboard sides, which introduce the complicated yaw moment. Moreover, its mechanism is very complicated and the hydrodynamic data are also limited comparing with conventional single propeller and single rudder ships.