A theoretical study is made first on the transmission and reflection waves past 2-D general antisymmetric floating bodies which are oscillating in response to regular incident waves. As a result, the ‘reverse’ theorem for the transmission and reflection coefficients and the wave-energy splitting theorem for the symmetric and antisymmetric wave components are derived for a general case of the motions of an antisymmetric body being free. Depending on the number and location of the fins, there exist one or two frequencies at which zero wave transmission can be realized. With this fact, it is suggested that the transmission wave can be small over the frequency range of our interest by optimizing the number, size, and location of horizontal fins attached to a rectangular-shaped main body.


There is a practical demand that floating breakwaters or piers (hereafter described generically as breakwaters) with high performance in the wave reflection should be developed and installed near the mouth of a marina to protect yachts or other small vessels from waves incoming from the open sea or generated by a high-speed boat running in proximity. From a viewpoint of preservation of water by exchanging with fresh water, floating-type breakwaters may be preferable. In fact, there have been many studies so far for the development of floating breakwaters using various ideas, and most of them were moored by slack chains anchored to the sea bottom. However, in the present study, it is required that the water depth is relatively shallow and floating breakwaters to be developed must not move horizontally to avoid collision with vessels in the marina; that is, floating breakwaters may be restricted to move only in heave by a number of vertical piles mounted to the sea bottom.

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