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Martins K., Blenkinsopp C. E., Almar Rafaël, Zang J. (2017). The influence of swash-based reflection on surf zone hydrodynamics : a wave-by-wave approach. Coastal Engineering, 122, 27-43. ISSN 0378-3839

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Lien direct chez l'éditeur doi:10.1016/j.coastaleng.2017.01.006

Titre
The influence of swash-based reflection on surf zone hydrodynamics : a wave-by-wave approach
Année de publication2017
Type de documentArticle référencé dans le Web of Science WOS:000400199100003
AuteursMartins K., Blenkinsopp C. E., Almar Rafaël, Zang J.
SourceCoastal Engineering, 2017, 122, p. 27-43. ISSN 0378-3839
RésuméA detailed understanding of the behaviour of waves in the nearshore is essential for coastal engineers as these waves cause beach erosion, coastal flooding and damage to coastal structures. Significantly, the influence of reflected waves is often neglected in surf zone studies, although they are known to influence wave properties and circulation in the nearshore. In this paper, a phase-resolving model is rigorously applied to model conditions from the prototype-scale BARDEXII experiment in order to examine and assess the influence of swash-based reflection on surf zone hydrodynamics at both the individual wave and time-averaged timescales. Surface elevation is separated into incoming and outgoing signals using the Radon Transform and a crest tracking algorithm is used to extract incident and reflected wave properties. It is found that on steep beaches (tan beta > 1: 9) the swash-based reflection - the reflection generated in the swash during the backwash contributes significantly to the intrawave variability of individual wave properties such as the wave height to water depth ratio gamma, through the generation of quasi-nodes/antinodes system. For gamma expressed with individual wave heights, variations up to 25% and 40% are obtained for the modelled regular and irregular wave tests, whereas it reaches 15% when it is based on the significant wave height. The outgoing wave field-induced hydrodynamics is also found to affect time-averaged parameters: undertow and horizontal velocity skewness. The undertow is mainly strengthened, particularly in the shoaling region where the outgoing component dominates over the contribution from the incoming wave field. Offshore of the bar, an onshore-directed flow streaming close to the bed is also generated under the outgoing wave field, and is suspected to help in stabilising the bar position. This, along with the influence of the outgoing wave field on the horizontal velocity skewness and the presence of quasi-standing waves, suggests a complex contribution of the hydrodynamics induced by swash-based reflection into sediment transport rates and nearshore bar generation/migration.
Plan de classementLimnologie physique / Océanographie physique [032] ; Sciences fondamentales / Techniques d'analyse et de recherche [020]
LocalisationFonds IRD [F B010069973]
Identifiant IRDfdi:010069973
Lien permanenthttp://www.documentation.ird.fr/hor/fdi:010069973

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