2002 年 2002 巻 238 号 p. 238_9-238_16
An apparatus of exciting a wave-suppressor plate usually equipped at outlet top of a circulating water channel (CWC) in heave and pitch motion is devised for making a progressive wave system with only one wave length on the water surface of a uniform flow in the CWC in order to conduct ship model performance test in waves. As well known an oscillating body in a uniform flow makes generally four progressive wave systems or two systems, the wave number being α1 (following wave) and α2 (head wave), in usual test conditions for model ships. At first a numerical simulation is performed by applying the two-dimensional linear theory of an oscillating planing plate to confirm possibility of making α1-wave disappear and of generating α2-wave only and to obtain α1-wave-free condition of combination of heaving and pitching of the wave-suppressor-plate. Next, experiments are conducted in a small CWC after developing a method of separating α1- and α2-components from the measured envelop of beating waves generated by the oscillating suppressor-plate. Through some iterations of a process of getting α1-wave-free condition of oscillation combination of the wave-suppressor-plate from the two experiments of different combinations, wave fields consisting of only α2-wave are obtained for three frequencies (3,4 and 5Hz) and two amplitudes at three velocities (0.5∼1.0m/s). Though these α1-wave-free results do not correspond very well with the simulations mainly due to the non-linearity of the real motion of the wave-suppressor-plate, it is concluded that more accumulation of experimental data makes this type of wave maker generate any progressive wave system with single wave length in CWC.
