A Theory of Wave Devouring Propulsion (2nd Report)

Optimized Foil Motions for a Passive-Type Wave Devouring Propulsor

抄録

In the previous report, a possibility of wave devouring propulsion was discussed qualitatively under the assumption that wave energy is ideally converted into thrust. Furthermore, as a realization of wave devouring propulsion, thrust generation by an oscillatory hydrofoil was discussed on the basis of Wu's theory. And free surface effects which had been neglected in Wu's theory were introduced approximately, and the importance of the free surface effects was pointed out with the results for a linear Wells turbine (non-oscillatory hydrofoil).
In the present report, a possibility of the idealized wave devouring propulsion is treated more quantitatively, and the advance speed effect on the wave drift force is correctly introduced under the assumption of the perfect absorption of wave energy.
As a main subject of the present report, a concept of power free motions of a hydrofoil in a wave is explained as a basis of passive-type wave devouring propulsion, and it is discussed how to choose an optimized motion among the power free motions. And the importance of the optimized motion is strongly demonstrated. Similar results have already been obtained for thrust constant motions by Wu.
The effect of depth of submergence on wave devouring efficiency of a linear Wells turbine is also discussed, and a possibility of an optimum depth of submergence is suggested.