Titre/Title :
Laboratory experiments on internal wave beams : transport and
attractors.
Contact :
Nicolas Grisouard (ERES)
Résumé/Abstract :
Stratified fluids support oblique internal wave beams. I will consider the question if these beams transport tracers and enhance mixing. I will present proof, from theory and laboratory experiments, that internal wave beams indeed drive transport, both horizontally and vertically, and consequently contribute to mixing. The transport is caused by the localised shear motion in the beam and is in a direction opposite to
that of the energy propagation. The discovery of this transport establishes that in stratified fluids enhanced vertical mixing takes place near internal wave beams, even when their amplitude is small. Internal waves provide a source of energy for mixing in the deep sea. At locations with rough topography these internal waves often take the
shape of beams. The transport found provides insight in the causes of spatial inhomogeneities in vertical mixing in general and in the dynamics of sediments and nutrients near rough topography in particular. We observe the transport of the tracers on an internal wave attractor. These attractors are known to play a role in the dynamics of rotating stars. This finding therefore suggests that in rotating stars strong transport of chemicals might take place along attractors.