Two Innovations for Improving Harbor Resonators

The results of an experimental study on two aspects of resonator behavior for harbor entrances are presented. The first aspect involves a battery of three resonators tuned to cover a wide frequency band. It is found that the efficacy of the battery is improved by increasing the distance along the main entrance channel between the individual resonators. An approximate method is presented for estimating the frequency of the most resonant peaks in the response of a battery to a flat incident wave spectrum. The method is a based on previous results. The second aspect investigated is that of nonuniform depths in the resonator configuration. If the still water depth in the resonator is reduced, the length of the resonator for resonance is considerably reduced. This will allow savings in capital expenditure on breakwaters incorporating rectangular resonators, and on excavating the resonators. However, the efficiency of the resonator is also impaired.