A Theory of Wave Devouring Propulsion (4th Report)

Abstract

In the previous report, thrust generation through absorption of wave energy by a passive-type hydrofoil propulsor was verified experimentally. Some theoretical studies are also conducted on the basis of Wu's theory for an unsteady hydrofoil in a wave . In the previous report, the experiments were conducted in a rather short wave range. So, the experimental apparatus and model have been improved, and the experiments in a long wave range are conducted in the present report. The experimental results are compared, more widely than in the previous report, with the theoretical ones obtained by the above mentioned theory. An application of the theory to cases where the foil draft is very small as in the present study may be doubtful, since the theory neglect the free surface effect completely. The theory, nevertheless, gives a correlation with the experiment better than expected, when the advance speed is not small. Effects of foil draft, heave and pitch springs and an auxiliary float are also investigated theoretically by applying the theory. Effects of wave making damping on thrust and motion of a foil are also studied. by introducing wave making damping terms into equations of foil motion approximately.