2017 Volume 12 Issue 2 Pages JFST0017
A two-dimensional ship propulsion model using the Weis-Fogh mechanism is analyzed by the potential flow theory and the conformal mapping. The purpose of this study is to clarify the most effective operating condition in which the loss is minimum. The opening and the closing stages are carefully studied. In both stages, a fixed point of the wing moves in the direction perpendicular to the flow direction. The condition to prevent the vortex shedding when the wing separates from the wall is to equalize the both sides pressure at the trailing edge of the wing, and the acceleration of the wing motion satisfying the condition is clarified. On the other hand, in the closing stage the condition to satisfy the so-called Kutta condition is applied at the wing edge. This condition means that the wing prevents the separation nor generation of the jet which produces high thrust but more loss. The unsteady forces and the moment on the wing are also shown.