Rudder effectiveness and speed correction for scale model ship testing

Abstract

The authors once proposed a method, rudder effectiveness correction, to realize full-scale equivalent maneuvering motion using scale models with the auxiliary thruster developed by them. The method presumed a free-running model test with a constant propeller rate of revolution and approximated a constant value of rudder effective correction factor defined in a steady straight running condition. In this report the authors propose a detailed method ensuring more precisely the similarity of maneuvering motion than the former one. The detailed method takes into account the similarities both of the rudder effectiveness and speed response during maneuvering motion even in external forces. The time-varying control both of the propeller rate of revolution and the rudder effectiveness correction factor based on the new method enables scale model ships to realize the similar maneuvering motion to full-scale ships more accurately. Numerical simulations using the modular mathematical model of maneuvering motion clarifies how well the detailed method raises the precision of full-scale equivalent maneuvering motion in free-running model tests comparing with the former method.