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Communication Dans Un Congrès Année : 2012

Asymmetry and Skewness in the bottom boundary layer : Small scale experiments and numerical model

Résumé

This study investigates the non-linearities of wave boundary layer in the surf zone. It mainly focuses on the acceleration skewness or asymmetry. Experiments [e.g. Grasso et al., 2011] show that asymmetry influences the sediment transport. Its influence resides in the fact that asymmetry in velocity (acceleration skewness) tends to transform into velocity skewness within the boundary layer. Analysis by Henderson et al. [2004] predicts a linear relation between Sk _b/Sk and As /Sk where Sk _b is the non dimensional skewness near the bed, Sk the free-stream non-dimensional skewness and As the free-stream non-dimensional asymmetry. Numerous experiments were carried out in the LEGI wave flume over a mobile bed composed of lightweight sediments. The quasi-random forcing is a repetition of 2 concatenated bichromatic wave packets. Vertical profiles of velocity are measured in the surf zone. A clear linear relation is shown between these two ratios. The experimental results are compared with the numerical results. A linear relation between skewness and asymmetry is also obtained.
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Dates et versions

hal-00908879 , version 1 (16-05-2020)

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Céline Berni, Léandro Suarez Atias, Hervé Michallet, Eric Barthélemy. Asymmetry and Skewness in the bottom boundary layer : Small scale experiments and numerical model. 33rd International Conference on Coastal Engineering, Jul 2012, Santander, Spain. pp.waves.25, ⟨10.9753/icce.v33.waves.25⟩. ⟨hal-00908879⟩
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