Abstract
To accurately measure wave-overtopping quantity by each wave, visualization techniques and Particle Image Velocimetry(PIV) were applied to model experiments on wave overtoppings. First, the setting conditions of a high speed camera and a suitable tracer for visualization of wave overtoppings were investigated. Second, a measurement technique of wave-overtoppings was discussed. In this technique, vertical velocity vectors of the fluid running up and down in front of a seawall are measured by PIV. The wave-overtopping quantity, then, is calculated based on the integration of the vertical velocity vectors. Finally, the accuracy of the proposed technique was verified by comparing it with a conventional technique with a measuring box which can be applied to only simple regular wave cases.
The main conclusions are as follows: 1) The investigation of small particles as a tracer showed that micro bubbles are the most appropriate for visualization of wave-overtoppings in model experiments. 2) The frame rate of 400 fps and the shutter speed of 1/500s are the best conditions of a high speed camera to record the wave run-ups. 3) When wave overtopping quantity (q) is larger than 10-3(m3/(ms)), it becomes possible to measure q accurately by using PIV.
