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Accueil > Actualités > Séminaires > Séminaires 2011

Séminaire vendredi 27 mai à 10h, salle A103 du LEGI

Fabrice VERON, Associate Professor School of Marine Science and Policy, University of Delaware, USA.

Titre/Title :
Air-flow separation and spray generation above short and steep waves at high wind speeds.

Contact :
Chantal Staquet

Résumé/Abstract :
In sufficiently high wind speed conditions, breaking of small, steep waves at the surface of natural water bodies become significant and lead to several related phenomena which affect the multiple air-water fluxes through different pathways. First, similarly to the flow past solid, fixed obstacles, the airflow occasionally separates from the water surface. Our laboratory experiments show dramatic variations of the near-surface viscous stress along with
significant generation of vorticity. Modeling of the phenomenon and its effect on the mean flow leads to an effective reduction of the total air water drag coefficient. Concurrently, water also separates from the interface to form a substantial number of spray drops. Although consensus around the qualitative
impacts of these drops has been building in recent years, the quantification of the spray mediated fluxes of momentum, heat and mass in the natural environment has remained elusive. Ultimately, the spray mediated fluxes depend on three controlling factors : the number and size of drops formed at the interface, the duration of suspension within the atmospheric boundary layer, and the transfer rates between the drops and the air. With a combination of laboratory
measurements and Lagrangian stochastic simulations, we find somewhat lower
spray-mediated fluxes than previously reported. Our results have implications on the generation and transport of marine aerosols and raise new questions about the development and sustainment of tropical storms and hurricanes.