In this study, fluid motions in the joint gap of caisson-type breakwater are investigated experimentally. This study focuses on a random wave attack as incident wave and discusses: 1) whether fluid resonance occurs in the gap; 2) the conditions at which fluid resonance occurs; 3) the scale of wave heights in the gaps at the resonance.
In the experiments, fluid resonance occurred in the gap under random wave as fluid resonance happened under monochromatic waves. The appearance of fluid resonance under random waves depended on the resonant frequency at which fluid resonance occurred under monochromatic waves. Furthermore, the amplification of wave height in the gap was linearly proportional to the relative frequency spectrum at the resonant frequency.