Investigation on the rudder force of a ship in large drifting conditions with the MMG model

Abstract

The rudder force, including interference with a ship hull in large drifting conditions, is investigated in this study by captive model tests using a ship model with steering. In the tests, hydrodynamic forces acting on the ship, the rudder normal force, and propeller thrust are measured while changing the hull drift angle $$\beta $$ in the range of $$-180^{\circ } \sim 180^{\circ }$$ , which encompasses forward, lateral, and astern motion. The hull and rudder interaction coefficients, thrust deduction factor, inflow velocity to propeller, and inflow velocity to rudder are obtained in large drifting conditions using the measured hydrodynamic force data. The Maneuvering Model Group (MMG) model (Yasukawa and Yoshimura, 2015) is applicable for estimating the rudder force when the absolute value of $$\beta $$ is smaller than $$45^\circ $$ . In this region, the hydrodynamic force parameters for the inflow velocity to the rudder are nearly constant for any hull drift angle. However, in the region where the absolute value of $$\beta $$ is greater than nearly $$45^\circ $$ , the MMG model cannot be applied. For improving the formula for the longitudinal inflow velocity component to the rudder ( $$u_R$$ ), we propose a new formula that is applicable to any hull drift angle.