An experimental study on wave run-ups of fixed four-rounded-square-column array in focused waves

The wave run-up along the column surface is one of the focal issues of research in ocean engineering. This experimental study aimed to reveal the wave run-up characteristics of a fixed four-square-column array with rounded corners under focused waves by controlling wave steepness, spectral peak period, wave direction, and focus position. The experiment utilized a 1:50 scale physical model, with focused waves generated in a wave tank to simulate extreme sea conditions. Four squared columns were fixed to the tank carriage. Eighteen wave probes were installed around the fore and rear columns to measure wave run-ups. The results indicated that with an increase in wave steepness, the wave run-up ratio demonstrates an increasing trend, particularly when the waves approach or precisely break at the focal point. Furthermore, the wave run-up ratio on the front column decreases as the spectral peak period increases, owing to the weakening of the nonlinear wave-column interaction when the wavelength is significantly larger than the column width. For the rear column, the dissipation of wave energy by the front column leads to a notably lower wave run-up ratio. However, under the influence of incident focused waves at certain wavelengths, the rear column may experience a more intense secondary run-up phenomenon. Additionally, comparative analysis of different focus positions revealed that the wave run-up ratio is maximized when the focus position is located behind the front column. The incident waves at 45° were diffracted by the rounded corners of the columns, leading to the dispersion of wave energy and consequently yielding a reduced wave run-up ratio. The experimental data obtained serve as crucial benchmarks for validating further numerical simulations of wave impact on rounded square columns.