Experimental study on wave pressure distribution of the twin-plate breakwater under freak waves

This study carried out extensive experiments to investigate the wave loads on the twin-plate breakwater under freak waves. The characteristics of wave forces were checked under various relative plate width, relative wave height as well as freak waves parameters. The results show that the maximum wave pressure occurred on the offshore side of the twin-plate, and decreased along the wave propagating direction. The wave pressures on the four surfaces of the twin-plate showed significant difference in both magnitude and phase, and the phase difference ranged in 0.1T_p~0.4T_p. In addition, the measured maximum wave pressure and total vertical force on the twin-plate were compared to those under irregular waves. There is no significant difference in the distribution of the wave pressure envelop for irregular and freak waves. However, the magnitude under freak waves is significant larger than that under irregular waves. Basically, the ratio of the maximum total uplift forces for under freak waves to irregular waves ranges in 1.06-2.45; the ratio of the maximum downward vertical force ranges in 1.22 to 2.07. The increment of the maximum wave pressure is subjected to the freak waves parameter α₁.With α₁ from 2.04 to 3.1, the maximum pressures under freak waves can be 20% to 80% larger than those under irregular waves. The ratio of the maximum wave suction force between the irregular and freak waves is decreased with α₄. With α₄=0.62-0.75, the ratio of the maximum wave suction force changes from 1.61 to 0.87. It should be noted that, the critical value of α₄ turns out to be 0.72, below which the maximum wave suction forces under freak waves are larger than those under irregular waves, and above which is the other way round.