This paper proposed novel technique of 3-D wave field measurement using reflected light image. The greatest benefit of this method is that special treatments like seeding or dyeing are not required to make the water surface visible. For basic research, steady waves around the Wigley hull model were measured in the towing tank of Osaka University.
Image measurement techniques have been developed in many different fields to verify the detailed data obtained by CFD. In previous studies, several image measurement techniques have been proposed to obtain wave patterns and height distribution: Stereo camera method, grid projection method (Kanai, 1984) and projected light distribution method (PLD method) using the law of refraction (Suzuki and Sumino, 1993). The advantage of these methods is that a huge amount of detailed data in a two-dimensional plane can be obtained at once. This was impossible with the conventional wave height meters that measured only one point at once. Also, because with the new methods we can obtain the wave patterns on a two-dimensional plane continuously; it is possible to observe unsteady wave distributions in a time sequence. Hence, the newly developed image measurement techniques provide more efficient ways in the investigation of unsteady wave distribution. On the other hand, they have some difficulties for practical use in a large towing tank. In the stereo camera method and the grid projection method, seeding material are required to make the water surface visible. In the PLD method, the setup of a light source under the water is quite difficult. Therefore, we need a new imaging technique to measure wave height distributions. Our group has been developing a reflected light distribution method (RLD method) for some years (Sanada et al.,2006).This is the image based measurement technique to use reflection image from the diffuse light source by the water surface.
