A Study On The Maneuverability Of Twin Screw And Twin Rudder Vessel

With increasingly development of large twin-screw and twin-rudder vessels, it becomes more and more necessary to investigate the maneuverability of such vessels. In this paper, the maneuverability of the twin-screw and twin-rudder vessel in the harbor handling without tug assistance has been theoretically investigated based on establishing the maneuvering mathematical model of twin-screw and twin-rudder vessel and was expected to provide reference for officers and pilots.This paper contains five parts. In the first part, the background and significant of this investigation, present condition of the researches on the maneuverability of twin-screw and twin-rudder vessel worldwide and the proposed method for researching in this paper were introduced. In the second part, according to the MMG's separated modeling theory, a ship maneuvering mathematical model for twin-screw and twin-rudder vessel has been established based on the mathematical model for single-screwed vessel by taking account of the characteristics of the twin-screw and twin-rudder vessel, amending the coefficients of hull wake factor, interference among the hull, propeller and rudder. In the third part, a ship-in-harbor maneuvering mathematical model under the condition of shallow water and low speed has been established based on the aforesaid works taking account of the effect of shallow water, low speed and large drift angle. In the fourth part, the above-established mathematical model has been checked by comparing the simulated results and trial results. In addition, the ship handling in the harbor of a twin-screw and twin-rudder vessel also has been simulated using above mathematical model.Through the investigation, the following results has been achieved: (1) Maneuvering mathematical model for the twin-screw and twin-rudder vessel has been established. By comparing the simulated results with the trial results, it is sounded that the mathematical model established has a preferable precision and can be applied to simulate the ship's maneuvering motion in the harbor for the twin-screw and twin-rudder vessels.(2) The berthing and un-berthing simulation result of a twin-screw and twin-rudder vessel indicated that: the push-pull mode can be induced when the ship's speed was less than 5 knots, on the other hand, when the ship's speed was more than 5 knots, the efficiency of the bow thruster was decreased to 40%power or more. So the push-pull mode does not successfully applied, furthermore, the ability of push-pull maneuvering mode can maintained against the wind force 6.The ship maneuvering mathematical model established in this paper can show the maneuvering characteristics for the twin-screw and twin-rudder vessels. The simulated maneuverability of the twin-screw and twin-rudder vessel in the harbor can provide reference for officers and pilots when they handle twin-screw and twin-rudder vessels in the harbor.