Study on Hydroelasticity for Realization of Very Large Floating Structures

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(1) A new calculation method was developed for a column-supported very large floating structure, in which the elastic deflection of the upper deck was represented by a superposition of natural modes of a rectangular thin plate, and hydrodynamic interactions among a great number of supporting columns were correctly taken into account.(2) Model experiments have been conducted using 64 vertical circular cylinders arranged in 4 rows and 16 columns with equal separation distance. Measured were hydrodynamic forces on some of individual cylinders and the wave elevation along the center line of the structure. Measured results were in good agreement with the computed results by the newly-developed hierarchical interaction theory.(3) Two different calculation methods were developed for computing the wave drift force and moment on a column-supported very large floating structure. One is the so-called "far-field" method based on the momentum-conservation principle, and the other is the "near-field" method by the direct pressure integration.The drift force on the whole 64 cylinders was precisely predicted by both methods, confirming the validity of both numerical methods. The local steady forces on each cylinder were also measured and the results were in good agreement with computed results by the "near-field" method.(4) A time-domain calculation method was developed for evaluating transient elastic responses of a pontoon-type floating structure due to the take-off and landing of airplanes. Special efforts were devoted to the numerical accuracy and efficiency. Computed results were compared with measurements at the Ship Research Institute, which showed very good agreement confirming the validity of the developed numerical scheme.