NUMERICAL MODELLING OF BREAKER DEPTH INDEX

Abstract

The breaker depth index, γb, is commonly used to determine the wave height to water depth ratio where the wave will break (Horikawa, 1988). In the present study, γb has been calculated using a fully nonlinear Boussinesq Type Equations (BTE) wave model with implemented BCI (Breaking Celerity Index). The BCI is a phase-resolving type breaking criterion for calculating the incipient wave breaking conditions (D’Alessandro and Tomasicchio, 2008). The model suitability in predicting γb has been verified against physical data from an experimental investigation conducted with incident regular waves propagating along uniform 1:20 and 1:50 slope beaches (G.V. dos Reis, 1992), and estimates of γb from five existing empirical formulae (Battjes, 1974; Ostendorf and Madsen, 1979; Singamsetti and Wind, 1980; Smith and Kraus, 1990; Goda, 2010). The comparisons showed that BCI presents a better agreement with the physical data with respect to the other investigated formulae in determining the value of γb, independently from the breaker type. In addition, the verification of the BCI in determining γb has been extended to the observed data from a large-scale laboratory experiment on wave hydrodynamics performed over a fixed-bed barred beach (Tomasicchio and Sancho, 2002).