Pressure characteristics of void-fraction-classified plunging wave impacts on a rounded-square column

This is the authors' abstract. We don't add key points for this paper.

Breaking wave impacts can generate sudden and extreme loading, but the quantitative pressure differences among distinct impact types remain insufficiently understood. To characterise these differences, focused wave tests were conducted on a fixed rounded-square column. Six focused wave cases were classified into four impact types following a previously proposed void-fraction-based classification framework. The measured pressures were analysed in terms of pressure histories, time-frequency features, spatial distributions, pressure impulses, pressure rise times and peak-pressure probability distributions. The results show that Type I generated the lowest peak pressure, but its pressure impulse was comparable to those of the other impact types. Type II produced the most severe local pressures, with a rapid church-roof-like peak and decaying oscillations caused by direct plunging-tongue impact and trapped-air compression. Type III retained clear impulsive features, whereas Type IV was weakened by upstream breaking and aeration before impact. The impact component governed the main spatial differences among impact types, and the largest impulse did not always coincide with the largest peak pressure. Both Weibull and GEV distributions described the normalised peak pressures reasonably well. These findings support type-dependent assessment of breaking wave impact loads in model testing and design.