Numerical simulation of bubble-liquid interactions and sediment transport under breaking waves in the surf zone

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Monday 29 june 2015

17:42 - 17:45h at Mississippi (level 1)

Themes: (T) Sediment management and morphodynamics, (ST) Sediment transport mechanisms and modelling, Poster pitches

Parallel session: Poster pitch: 3A. Sediment - Erosion

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Sediment transport driven by waves and current plays an important role in the evolution of coastal morphology. Wave breaking is one of the most critical processes controlling sediment deposition and erosion in the surf zone. During the wave breaking process, a large volume of air enters into the water column and quickly evolves into bubble clouds that interact with the surrounding water. The flow turbulence is strongly influenced by the presence of bubbles, so is the associated sediment transport, which is still poorly understood. In this study, a two-dimensional numerical flume is developed to investigate the characteristics of the bubbly flow dynamics and air bubble evolution as well as the sediment transport under breaking waves in the surf zone. The numerical model consists of three basic modules, namely, the filtered two-phase bubble-liquid module, the bubble entrainment module and the sediment transport module. The results of breaking wave profiles, air bubble distribution and turbulence field are verified by existing experimental data and field measurements. It is found that the air bubble degassing rate (breaking) is very quick and induces a large amount of total energy dissipation in the breaking region. The suspended sediment concentration distributions and the net sediment transport rate during one breaking wave will be predicted by using the modeling results. The air bubbles' influence on sediment transport under breaking waves conditions will be qualified and analyzed by the comparison with results that provided by a one-phase model which has not considered the air bubble effects.