Performance Improvement of Weis-Fogh Type Ship’s Propulsion Mechanism Using a Wing Restrained by an Elastic Spring

Abstract

This study was conducted in an attempt to improve the hydrodynamic performance of a Weis-Fogh type ship propulsion mechanism by installing a spring to the wing so that the opening angle of the wing can be changed automatically. With the prototype design, the average thrust coefficient was almost fixed with all velocity ratios; but with the spring type, the thrust coefficient was increased sharply as the velocity ratio increased. The average propulsive efficiency was higher with a bigger opening angle in the prototype but in the spring type design, the one with a smaller spring coefficient had higher efficiency. In the case of velocity ratios over 1.5 where big thrust can be generated, the spring type had more than twice the increase in propulsion efficiency compared with the prototype.