Numerical Simulations of Waves Breaking over a Rectangular Submerged Reef Consisting of a Double Step: Analogies with massive Natural Wave Breaking over Abrupt Bathymetries

The aim of this article is not to study any practical design for a breakwater device nor to show the evidence of a particular event when waves break over a varying bathymetry, but to promote a paper showing an interesting idea of wave decomposition prior to impact, used in an experimental and numerical study published by Yasuda et al. (Proceedings 25th international conferences coastal engineering, pp 300–313, 1996) and Yasuda et al. (Coast Eng J 41(2): 269–280, 1999. We investigated the new type of breaker, proposed by Yasuda et al. (1996), by detailing several geometric aspects which lead to the unusual size and behavior of some very large plunging jets generated when waves break above some drastic changes of bathymetry. We thoroughly investigated all geometrical aspects of the breaking process, to propose a classification of the breaker types which were observed in our numerical results. We indicated the influences of the reef parameters (steps heights and lengths) on the subsequent breaking process. We also showed that the air entrainment was indeed much larger during the composite breaker occurrence