Maneuvering simulations of twin-propeller and twin-rudder ship in shallow water using equivalent single rudder model

An equivalent single rudder (ESR) model is presented for maneuvering simulations of twin-propeller and twin-rudder ships within the framework of the maneuvering modeling group (MMG) method Yasukawa (J Marine Sci Technol 20:37-52, 2015). It eliminates the complexity of a mathematical model by treating a port and starboard rudders as a single rudder located at the center of the ship hull. Specifically, an expression for the rudder force is presented using the ESR model. As examples, the results of captive model tests for a twin-screw ferry in deep and shallow water and the analysis results are presented, and maneuvering simulations are conducted using the hydrodynamic force coefficients obtained from the analysis. The simulation results of turning and zig-zag maneuvers agree with the results of free-running model tests, in regard to practical application. The maneuvering simulation method using the ESR model is validated for twin-propeller and twin-rudder ships in deep and shallow water.