Nonlinearities of short and long waves across the shoaling, surf and swash zones: large-scale physical model results
Résumé
In the scope of GLOBEX HYDRALAB IV project, laboratory experiments were performed in a 110-m-long beach, with a 1/80 rigid-bottom slope. With the free-surface elevation and cross-shore velocity data, the evolution of velocity nonlinearities along the profile (shoaling, surf and swash zones) is analyzed, both for short and long waves. To better investigate the different hydrodynamic processes at work, the third-order velocity moment terms are computed, and their relative importance along the profile is evaluated, relative to breakpoint position. Short-wave skewness, short-wave variance correlation to long-wave velocity and stirring by short waves and transport by mean flow were found to be the dominant terms outside the surf zone. Inside the surf zone, stirring by both short and long waves and subsequent transport offshore by the mean flow, and skewness of short waves were found to be the main driving mechanisms. In the swash zone, where long waves dominate, the third-order velocity moment terms tend to assume positive values. A thorough analysis of swash zone data processing and hydrodynamics is carried out and some of the current limitations of such processing are unraveled.