Abstract
Many wave energy absorption system proposed can absorb wave energy with high efficiency, regarding wave energy at a specified frequency band. But they have lower their absorption efficiency in irregular waves. This is due to the fact that while waves themselves are composed of wide-range frequencies. The natural frequency of the wave energy absorption system itself is basically a single one, and is so arranged that the wave absorption efficiency will become the greatest in the vicinity of its natural frequency. To overcome this discrepancy, ingenuity has been used to estimate the incident waves and functionally change the natural frequency, but this method has not yet been able to enhance the efficiency. This research verifies the existense of determining the natural frequency of the water column in the oscillating water-column-type wave energy absorption facility, using the same concept as that of the water column in the U-shaped tube. We confirmed the absorption efficiency at the case of installing plural number of water columns which have different natural frequencies in the same facility. In addition, this facility was able to absorb the wave energy of an irregular waves in real marine area.