Experimental characterisation of breaking wave impact loads on a vertical cylinder

This article presents experimental measurements of breaking wave impact loads on a vertical cylinder. The focus is on the influence of some of the breaking wave properties on the measured force. These properties are the distance to breaking, δ, defined as the distance between the breaking location and the front face of the cylinder, and the breaking strength, characterised here by the Γ parameter proposed by Derakhti et al. (2018). The wave characteristics are obtained through numerical simulations of the breaking waves using a fully non-linear potential flow solver. Seven breaking waves with different breaking strengths have been considered. For each wave, the distance to breaking has been systematically varied and the resulting impact force time-history was measured. It is found that except for the two less intense breaking cases, corresponding to values of Γ lower than one, there is a value of δ for which the magnitude of the impact force is maximum. Small variations of the distance to breaking δ strongly influence the impact force time-history and its maximum. A linear relationship is observed between the maximum force and the breaking strength Γ. For the wave cases with values of Γ higher than one, the maximum impact force is observed when the distance to breaking δ is close to 5 % of the wavelength. An empirical wave slamming coefficient accounting for the distance to breaking δ and the breaking strength Γ is derived.