Surf zone retention in a laboratory rip current

Abstract : 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.
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Article dans une revue
Journal of Coastal Research, Coastal Education and Research Foundation, 2011, SI 64, pp.50-54
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Contributeur : Hervé Michallet <>
Soumis le : lundi 5 décembre 2011 - 18:17:03
Dernière modification le : jeudi 3 janvier 2019 - 16:30:08

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Bruno Castelle, Hervé Michallet, Vincent Marieu, Philippe Bonneton. Surf zone retention in a laboratory rip current. Journal of Coastal Research, Coastal Education and Research Foundation, 2011, SI 64, pp.50-54. 〈hal-00648471〉

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