A Study on Mathematical Model for the Maneuvering Motions of Twin-propeller Twin-rudder Ship : In Reference to the Maneuvering Motion from Ordinary Speed Range to Low Speed Range

The estimation of maneuvering motion of twin-propeller & twin-rudder ship is not cleared still for the reason of its hydrodynamical complication. It is important to express in the interaction among the hull, propeller and rudder during maneuvering motion. In this paper, mathematical model for the maneuvering motion from ordinary speed range to low speed range are discussed. In order to know the characteristics of hull, propeller and rudder, the captive model tests are carried out for wide range concerning with yaw and sway motion. The mathematical models are examined by free running model test. The results of this study are as follows : 1) The wake ratio (1-w_P) and δ_R (rudder angle at normal force equal 0) under the maneuvering motion can not be defined by geometric drifting angle at rudder and propeller point. 2) Hydrodynamic forces acting on the hull are exactly expressed by two mathematical models classified by speed range. 3) Propeller thrust and rudder normal force are able to be divided effectively into four conditions according to the ship speed and propeller revolution. 4) The propeller thrust and rudder normal force are formulated effectively according to four conditions of propeller advance ratio.