Experimental analysis and numerical simulation of wave overtopping on a fixed vertical cylinder under regular waves

Abstract

Wave overtopping phenomenon affects relatively narrow offshore marine structures different from shoreline linear structures, where there is not defined a precise prediction methodology as it is the case of the behaviour at long coastal defences. In the present study a combined experimental and numerical approach has been followed to obtain an empirical relation that represents the relative overtopping discharge over a fixed vertical cylinder exposed to non-impulsive wave conditions. The phenomenon follows a Weibull type dependence on the relative freeboard in a similar way as the case of vertical walls but reporting a decreasing overtopping rate at higher freeboards. In addition, a direct linear relationship between the relative mean flow thickness computed at the centre of the circular crest of the cylinder and the relative overtopping discharge has been observed. This methodology may be used as an indirect cost-effective method to characterize experimentally the wave overtopping phenomenon in cylindrical structures of full-scale prototypes without the need of accumulating and characterising huge amounts of overtopped water volumes. The present study contains a systematic analysis of the dispersion obtained in the experimental and computational results to evaluate the performance attributed to the proposed empirical expressions. • Overtopping has been characterized in a fixed vertical cylinder and compared with the behaviour of long shoreline defences. • A RANS-VOF Eulerian numerical model has been validated experimentally with a physical scaled model in a wave flume. • A new Weibull type expression predicts the overtopping discharge in a vertical cylinder for non-impulsive wave conditions. • The flow thickness measured at the crest has been proposed to determine the mean overtopping discharge over the structure.