1. Surf zone retention in a laboratory rip current
- Author
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Castelle, B., Michallet, H., Vincent Marieu, Bonneton, P., Michallet, Hervé, Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Écoulements Géophysiques et Industriels [Grenoble] (LEGI), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), and MODLIT (RELIEFS/INSU, SHOM-DGA)
- Subjects
Drifters ,asymmetric rip current ,[PHYS.MECA.MEFL] Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph] ,[SPI.MECA.MEFL] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph] ,[PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph] ,Vortex shedding ,[SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph] - Abstract
Proceedings of the 11th International Coastal Symposium, Szczecin, Poland; International audience; Field and numerical studies recently challenged the traditional paradigm of rip currents systems that states that rip currents produce a continuous interchange of waters between the surf zone and shelf. Instead it is suggested that rip current flow fields consist of semi-enclosed, large-scale vortices that retain floating material (e.g. drifters) at a rate of about 80-90%. In this paper is presented a laboratory rip current experiment over eight contrasting nature-like beach morphologies involving deployment of a large number of drifters. When the rip current was symmetric over a typical bar and rip morphology (4 out of the 8 cases), only about 10% of the drifters entering the rip exited the surf zone, whereas when the mean rip current was asymmetric, more drifters (~30-45%) entering in the rip exited the surf zone compartment. Drifters exiting the surf zone compartment were not systematically caught by a pulsating jet. More frequently, these drifters were likely caught in a vortex being shed offshore, as they often looped track in the vicinity of the rip head before exiting the surfzone compartment. This confirms new thoughts on rip currents that are very important from the perspective of both mixing in the nearshore and beach safety: rip currents systems only sporadically produce intense interchange between the waters of the surf zone and the shelf. Results additionally suggest that asymmetric rip current retain less floating material than symmetric rip currents.