Analysis of Diffraction Waves Around a Ship Using Projected Light Distribution Method

Abstract

This paper is the second report that describes the capability of projected light distribution method to measure the diffraction waves generated by a ship operating in regular incident waves. In this method the waves are projected onto a screen as light distribution images and the images are recorded using a CCD Camera. In order to obtain diffraction waves, experiments were divided into two steps. Firstly, incident waves were measured. Secondly, the combination between incident waves with diffraction waves around a ship model was measured. The diffraction waves can then be obtained by subtracting incident wave images from combined one. The Kochin function was obtained using the same method as explained in the previous paper6). The results are evaluated by making some transverse cuts on the image data in the y-direction (transverse cut). The obtained Kochin functions are compared with the longitudinal cut results based on Ohkusu method, and also with theoretical results based on slender body theory. Using the results of Kochin Function, the wave pattern are recalculated and they are compared with the results of measurement using super sonic wave height meters.

Barrel Distortion Correction for Digital Optic-Based Motion Tracking in Ship Hydrodynamic Model Experiments

“…Other studies are motion tracking based on horizon detection, which are applied to measure ship attitude [8], to track ships in the open sea [9], and to develop navigation systems on autonomous ships [10]. Erwandi and Suzuki [11][12][13] proposed a low cost technique to measure the wave height caused by ship model motion in towing tank using digital video camera. The technique called as projected light distribution method to measure the unsteady wave generated by ship forced to oscillate in heave motion while the ship model moves forward in constant speed.…”