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Vorticity evolution and related low-frequency motions on a rip-current with a non-uniform alongshore wave forcing

Abstract : Experimental results on a rip formed over a heterogeneous beach with a mobile sandy bed are analyzed using a 2D depth-averaged Non Linear Shallow Water Equations (NSWE) model. The numerical model is validated comparing results with measured wave height values and velocity time series recorded by Acoustic Doppler Velocimeters (ADV) showing good agreement with experimental data. The numerical model is then used to produce a much longer simulation under the same conditions in order to obtain reliable information on the Very Low Frequency (VLF) band. By computing Hrms and Urms in this frequency band we are able to observe pulsations that correlate with the slow evolution of the rip current, and the contribution of the VLF to the vorticity dynamics. We also show that a peak of energy exists in the VLF range in the position of the center of the recirculation rip cell, and the rip-current offshore velocity. We analyze model results using time series and spectral analysis of free surface, velocities and vorticity. A large amount of energy in the VLF range is observed in the vorticity generated in the surf zone. By looking closer at one rip-vortex, we show that the position of the center of the recirculation cell moves with time scales in the VLF spectral range. The rip-current offshore velocity pulsates at VLF frequencies.
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https://hal.archives-ouvertes.fr/hal-00909143
Contributor : Hervé Michallet Connect in order to contact the contributor
Submitted on : Monday, November 25, 2013 - 8:38:53 PM
Last modification on : Friday, January 7, 2022 - 9:34:03 AM

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  • HAL Id : hal-00909143, version 1

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Léandro Suarez Atias, Rodrigo Cienfuegos, Eric Barthélemy, Hervé Michallet. Vorticity evolution and related low-frequency motions on a rip-current with a non-uniform alongshore wave forcing. 7th International Conference on Coastal Dynamics, Jun 2013, Arcachon, France. pp.1571 - 1580. ⟨hal-00909143⟩

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