Author(s): Nuele Terrile
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Abstract: To promote “vorticity-thinking” for the description in the nearshore region, its hydrodynamic circulation is investigated by means of a point-vortex approach similar in spirit, but more complete and suited to practical applications, to that of Kennedy (2003). Results have been obtained using a “typical” rip-current bathymetry for which we also test the model comparing the vorticity dynamics with the results obtained by means of both wave-resolved and waveaveraged circulation models. A comparison of dynamically-equivalent flow configurations shows that the dissipative point-vortex model solutions, neglecting any influence of the wave field, provide rip current velocities in good agreement with both types of numerical solutions. We also analyze in detail the enstrophy dissipation mechanisms for both wave-averaged, (SHORECIRC) and wave-resolving (FUNWAVE2D) models of wave-induced nearshore circulation. Enstrophy allows us to clearly identify sources/sinks terms by positive/negativedefinite contributions in the appropriate transport equations and it is taken as the most suitable indicator for assessing the model ’ s performances in describing flows characterized by largescale vortices. Both wave-averaged and wave-resolving computations clearly show that, apart from bottom friction, the most intense dissipation mechanism is due to classic viscous effects, while depth gradients weakly contribute
Year: 2007