Prediction of the Wave Run-Up on Pile Breakwaters

Pile breakwaters have been adopted in coastal regions with soft seabeds, owing to their advantageous features. They are subjected to wave run-ups, which would increase the wave transmission and threaten the superstructures above the piles (e.g., wharves, bridges, and pipelines). However, there are still no systematic design codes for this kind of structure. In this paper, an accurate prediction of the wave run-up on a pile breakwater is proposed, using a combined experimental-numerical approach. An experimental campaign comprising the effects of wave steepness, relative wave height, relative pile diameter, and blockage ratio is carried out by recording the run-up of both regular and irregular waves. A computational fluid dynamics (CFD) model is validated by the experimental data and then utilized to examine the hydrodynamic process. Two distinct patterns are identified by the localized flow field, which depend on the relationship between the pile diameter and the incident wavelength and lead to significant differences in the run-up height. By analyzing the experimental data set, a semiempirical formula is developed in the framework of the velocity stagnation head method, which gives satisfactory predictions to the run-up of both regular and irregular waves. The research outcome can provide a guideline for the structural design of a pile breakwater.