Free Running Model Experiment on Speed Loss in Directional Spectrum Waves

Abstract

For evaluating speed loss, self-propulsion test and free running test are carried out in directional spectrum waves with a full ship model in the towing tank of Yokohama National University. Such experiments will be the first time in the world. In the free running test, the model has six degrees of freedom as in real condition, and it is controlled to run straightly by using rudder controlling system, therefore the speed loss can be derived directly by considering the relative speed against carriage by using optical position sensor. It is found that the speed loss in short-crested waves is bigger than the speed loss in long-crested waves in short wave length. The experimental results of speed loss in directional spectrum waves are compared with the results of estimation methods which are originated from the added resistance obtained by experiment and theoretical calculation.