EXPERIMENTAL STUDY OF FLOW UNDER 3-D BREAKING WAVES OVER A SMOOTH BEACH

Wave tank measurements of three-dimensional wave breaking on a 1/15 sloping beach for incoming regular waves were performed using Particle Image Velocimetry (PIV) and Acoustic Doppler Velocimetry (ADV). Two cases of incoming regular waves were tested with a wave period of 1.5 s, which corresponds to a wavelength of 3.51 m at deep water, and wave heights of H=0.08 m and H=0.10 m. The three-dimensionality of wave breaking was initiated by the diffraction of the incoming waves on a part of the beach narrower than the wave tank. Free surface elevations were also measured at several locations along the beach centerline. In the surf zone, the free surface elevation timeseries resembles the typical "saw-tooth" profile. Instantaneous velocity vector fields show that velocity increases at the back face of the breaking wave, while it is minimized just below the surface roller. Along the slope centerline, period-averaged mean velocity profiles show the existence of a current with a shoreward direction, whose magnitude increases rapidly with the water depth, while at planes parallel to the centerline, period-averaged velocity profile are characterized by the present of a current with seaward direction whose magnitude decreases with water depth.