Time Mean Behavior of Large Full Ships in the Sea

Abstract

In this paper authors propose a practical method to estimate the time mean behavior of large full ships in the sea. The method includes the effects of wind and waves and considers the engine characteristics. In the sea, there are disturbing external forces acting on full large ships like the added resistance, the lateral force and the turning moment. Those forces can be treated as the steady forces. Also the hydrodynamic forces caused by the hull, the rudder and the propeller can be treated as the steady forces. With those forces and by considering the equilibrium of the engine and propeller torque, we can set up four equilibrium equations among hull, propeller, rudder and engine. Regarding the speed, the drift angle, the encounter rudder angle and the propeller revolution number in the equations as unknown variables, we can obtain those time mean values of the ship in the sea by solving the equilibrium equations mentioned above with an iteration method. As the results the time mean behavior of the ships in the sea can be estimated.