Abstract
This study analyzed the characteristic of cycloidal propellers with 'Karman & Sears theory' and 'the vortex method', modeling the movement of the propeller as rotation with pitching and heaving movements. The reduced frequency which decides the characteristics of unsteadiness depends on the ratio of the length of the blade to the ration radius. In unsteady flow, thrust increased and its direction changed as the reduced frequency increased. Thrust efficiency calculated by the unsteady theory showed lower value than that obtained from the quasi-steady theory. Thrust efficiency in unsteady flow decreased sharply as the attack angle increased.
