ABSTRACT:

Dynamic behaviors of a submerged tension-moored structure with a pressurized air-chamber under wave action and wave transformations are investigated theoretically and experimentally. The rolling, heaving and swaying of the floating structure, wave reflection and transmission, and air pressure in the chamber are theoretically formulated with consideration of the compressibility of air. The validity of the newly developed theory is verified by two-dimensional hydraulic experiments.

1. INTRODUCTION

So far, a lot of researches have been conducted on the dynamic responses of semi-submerged moored floating structures such as semi-submersible platforms (DeBoom, et al.,1983), floating breakwaters (Fugazza and Natale, 1988) and floating storage tanks (Naftzger and Chakrabarti, 1980), and wave transformations in the wave field. A lot of the useful information and knowledge for designing and constructing the structures have been accumulated. In contrast, very few researches on dynamic behaviors of submerged moored structure and wave transformation have been carried out and many problems are left to be solved. The submerged moored floating structure such as a submerged moored breakwater can control the wave reflection and transmission better than semi-submerged ones(Iwata, et al., 1988). In addition, the submerged structure is pointed out to be better than the semisubmerged structure in seascaping in the near shore zone, since the crown height of the former is bellow the sea level. With this background, this paper is intended to, deal with a submerged tension-moored structure having a pressurized air-chamber and to investigate theoretically and experimentally the dynamic responses of the structure to waves and wave transmission and reflection. The major advantage of the structure with the pressurized air-chamber lies in easy control of the natural frequency of the structure only by adjusting the air pressure in the air-chamber. Secondary, two-dimensional laboratory experiments are performed to discuss the validity of the proposed theory.

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