A comparison of ship maneuvering characteristics for rudders and podded propulsors

Abstract

A comparison of a high speed container ship using a rudder versus a podded propulsor is made to study replacing a rudder with a pod. A mathematical model is altered to simulate a ship operating with a rudder and with a pod to maneuver. The model incorporates the nonlinear maneuvering equations and couples the surge and sway forces, yaw and roll moment, and the roll angle induced during a steady turn with varying rudder and pod angles. The model uses the hydrodynamic derivatives and coefficients for a high speed container ship. The equations are numerically integrated in order to predict the roll angle, sway and surge velocities, and the ship's position in the xy-plane. Both transient and steady state results are utilized to quantify the relative efficiency of each system. The results are used as a preliminary study into replacing a rudder on a ship with a podded propulsor. The results indicate that the ship responds faster and has a shorter turning radius with the pod at lower initial speeds and pod angles, while the rudder responds better at high speeds regardless of angle. Further research is necessary to study the effects of changing the pod's position and increasing the number of pods used.