The maximum influence of wind on wave overtopping at rubble mound breakwaters with crest walls under oblique wave attack

Abstract

The objective of this study is to assess the maximum influence of wind on wave overtopping at rubble mound breakwaters with crest walls under oblique wave attack. Physical model experiments were conducted in which the maximum effect of wind was simulated by placing a rotating paddle wheel on top of the crest wall. This paddle wheel mechanically transported water onshore that would otherwise fall back into the sea after colliding with the crest wall. In this manner, the maximum influence of wind can be calculated as the ratio of the mean overtopping discharge measured during tests with the rotating paddle wheel deployed to the mean discharge measured during reference wave overtopping tests. An adaptation of the existing expression that predicts the maximum effect of wind on wave overtopping was proposed to account for oblique wave incidence. The maximum influence of wind was also assessed in terms of individual overtopping volumes. The analysis revealed that, similar to discharges, the influence of wind is greater for smaller volumes and gradually decreases for larger volumes. The wind influence factor can be applied directly to overtopping discharges measured in physical or numerical flumes to estimate the mean discharge under the maximum influence of wind, as the wind was not modelled directly. This approach yields the maximum influence of wind on wave overtopping making the scaling of wind no longer relevant. Lastly, overtopping rates for oblique wave attack were compared to existing empirical formulae used for design purposes.