Citation

Bonneton N, Sous D, Bonneton P, Sommeria J. J. Coast. Res. 2006; (SI 39): 682-686.

Copyright

(Copyright © 2006, The Coastal Education and Research Foundation)

DOI

10.2307/25741664

PMID

unavailable

Abstract

In spite of the ubiquity of long shore flows, rip currents and also tidal jets in the near shore, large-scale vortices associated with these phenomena remain poorly understood. In particular, little is known about the effect of the vertical confinement on vortex dynamics. To understand this phenomenon we present in this paper a new laboratory experiment on pulsed jets (assimilated to a rip current) in a shallow water layer. In this study we analyze the evolution of three-dimensional turbulence generated by a pulsed jet in a homogeneous shallow water layer. We show that the jet evolution depends meanly on one dimensionless parameter c = (√Q/H²) tinj (where Qtinj the injected momentum flux, H the water depth and the injection duration). C characterizes the vertical confinement. When C is weak, the jet spreading is free. The generated turbulence remains fully three-dimensional. When C is large (C>2), we observe a damping of the vertical motion and the formation of a large horizontal dipolar structure. We also identify inside the global 2D dipolar structure, local three dimensional vortices. We have developed a theoretical model in good agreement with these measurements.
Keywords: Drowning; Drowning Prevention; Water Safety