FLUID RESONANCE IN NARROW GAPS OF VERY LARGE FLOATING STRUCTURE COMPOSED OF RECTANGULAR MODULES

摘要

Fluid resonance in narrow gaps of very large floating structure is investigated experimentally and theoretically. Especially, this study focus on the case of three rectangular modules with two gaps in order to make clear the difference with the case of one gap in which the authors (Saitoh et. al., 2003, 2006) have already had the experimental confirmation of occurrence of fluid resonance in the gap. Appearance conditions of fluid resonance are derived using the conservation of energy in the gaps and around two modules on the side of incident wave. In the derivation, first, two natural frequencies in the gaps are led as the frequencies described by the gravity acceleration and the geometrical conditions of floating structure including a water depth. Then, the appearance conditions are obtained substituting a dispersion relation of incident wave into the natural frequencies as kl1,2 tanh kh = 1 (k is the incident wave number, l1,2 : l1, l2 are the geometrical conditions, h is the water depth). The validity of the appearance conditions are verified by the comparison with the experimental results.