Laboratory experiment on waves propagating and breaking on a beach : regular and solitary waves
Résumé
Particle Image Velocimetry (PIV) measurements were performed in a wave tank underwater waves propagating and breaking on a 1/15 sloping beach. The wave shoaling occurredin the surf zone over a large domain covering several wave wavelengths fromincipient breaking up to swash zone beyond the shoreline. PIV spatial interrogationwindows have to be small enough to obtain accurate velocities, and one window coveronly a small part of the domain. To overcome this problem and to measure instantaneousvelocity field over the whole surf zone area, we have split the full field intotwelve overlapping smaller windows of same sizes. Local measurements were synchronizedto each other using pulsed TTL triggers and wave gauge data. The fullvelocity field was then reconstructed at every time step by gathering the twelve PIVfields. We measured then the complete space-time evolution of velocity field over thewhole surf zone.We calculated instantaneous, mean and fluctuating components of thevelocity and transport fields. We estimated an average air-water mixing ratio in eachpoint of the surf zone. We determined also the ensemble-period-average and phaseaveragecomponents of the flow with their associated fluctuating parts. The same experimentaltechnique was applied to the propagation of a Tanaka-like solitary wavebreaking on a sloping beach.