Wave-free floating-body forms in shallow water and application to a very large floating structure

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Some wave-free floating-body forms in heaving oscillation are obtained by using a wave-free singularity of source and vertical dipole combination to generate bulbous-shaped two-and three-dimentional bodies in shallow water. Body forms are obtained by the streamline tracing method at a planned wave frequency, where the body boundary condition of heaving oscillation is satisfied.Effects of location of the wave-free singularity and water depth on the body-form are studied. Body forms become slender as water depth becomes shallow. Wave exciting forces of obtained bodies are calculated by the singularity distribution method in two-and three-dimentions to verify that they become wave-free at the planned wave-number.Model experiments were conducted in 2D and 3D wave tanks. Wave exciting forces of obtained wave-free bodies were measured in regular waves. Wave-free frequency estimated by amplitude reaponse function of heaving excitation is almost same as the theory but a little bit higher, which may be attributed to nonlinear effects such as viscosity of water. Finally, some proposal are made to apply such a wave-free body to a very large floating structure (VLFS) of semi-submersible type.