ABOUT SOME UNCERTAINTIES IN THE PHYSICAL AND NUMERICAL MODELING OF WAVE OVERTOPPING OVER COASTAL STRUCTURES

This paper presents an experimental and numerical study aimed at gaining insight on the variability in the wave overtopping discharge on different types of coastal structures caused by different random starting phases of incident wave sequences sharing the same energy density spectrum. The experiments on a simple rubble mound breakwater have been carried out in the wave flume of the Roma Tre University (Rome, Italy). More than 150 small scale laboratory tests were carried out to simulate spectra producing different levels of overtopping. The numerical simulations, aimed at studying the wave overtopping on a simple impermeable smooth dike, have been carried out at the University of Nottingham (Nottingham, UK). More than 4000 simulations have been performed in order to provide a statistically robust dataset. For both the physical model tests and the numerical simulations the seeding of the random number generator used for the starting phases distribution was changed a number of times for each repetition of the same wave condition. The study allowed to quantify how the variability in the wave overtopping grows as the dimensionless freeboard increases and as the number of overtopping waves decreases.