Characterizing the wave loading on closely arranged pile breakwaters under regular and irregular waves

Pile breakwaters have been widely applied to protect harbors and coastal regions from extreme waves. To ensure the survivability of pile breakwaters in harsh sea conditions, an accurate estimate of the maximum wave loading is essential for structural design. In this paper, a series of experiments considering the effects of wave steepness, relative wave height, relative pile diameter, and relative pile distance are conducted to measure the loading of regular and irregular waves on pile breakwaters. Moreover, a high-fidelity numerical solver is comprehensively validated against the experimental data and then utilized to reveal the process of wave–pile interactions. Two distinct flow patterns relying on the relationship between the pile diameter D and the wavelength L are identified, which lead to different wave loading characteristics. By evaluating the performance of different approaches in analyzing the maximum wave force, the “wave force approach” is adopted by introducing a pile group coefficient Kgroup to account for the magnification of wave force compared with a single pile. Finally, a predictive model for Kgroup of pile breakwaters is developed based on the experimental data, which is proved to be applicable for regular and irregular unidirectional waves orthogonal to the piles.