ESTUDIO EXPERIMENTAL DEL MECANISMO DE GENERACIÓN DE ONDAS LARGAS EN UNA PLAYA DE PENDIENTE SUAVE

Abstract

The natural generation of infragravity waves in the nearshore zone can compromise the operability of ports and even influence sediment transport and beach morphodynamics. Under an irregular wave field, these long waves are associated to a slow modulation of the mean free surface level produced by wave groups, or alternatively by the quasi-periodic motion of the breaking point and the set-up level in the surf zone. The eventual amplification of these infragravity waves will be determined by the bathymetry in open bays, or by the bathymetry and the geometry in protected areas.

To investigate natural infragravity wave generation mechanisms, measurements were conducted in a wave flume prepared with 23 meters of flat bottom followed by 47 meters of a 1/80 mild slope beach. A random JONSWAP type wave field was forced and measurements of the free surface displacements were performed all over its length at high spatial resolution. Spatio-temporal correlation maps between wave group envelopes and infragravity waves, and spectral analysis on temporal series were produced in order to identify long wave dynamics and generation in the experimental set-up.