Image Measurement of Wave Height Distribution around High Speed Craft

Abstract

An image measurement system for wave height distribution has been developed. The system was applied to the wave measurement behind high speed craft. A number of small bubbles in water causes difference of light scattering between air and water. When a sheet laser illumination was given from the bottom of tank, the free surface is observed as the boundary of bright and dark area on the visualized image. The differential of the image data gives the position of free surface on the sheet illumination. The wave height distribution is obtained by changing the relative position of model and sheet illumination. Wave patterns around high-speed craft with several trim angles and sinkages are obtained. The wave patterns show that the undulation of free surface becomes gentle according to the decrease of sinkage in same trim angle. The difference of wave pattern with the trim angle is small in the present measurement range.