Laboratoire de Mécanique des Fluides et d'Acoustique - UMR 5509

LMFA - UMR 5509
Laboratoire de Mécanique des Fluides et d’Acoustique
Lyon
France


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Accueil > Pages perso > Micard Diane > Interaction between Internal Waves and a Column of Sediments

Interaction between Internal Waves and a Column of Particles

Master

This work has been done during my master thesis at ENS Lyon and directed by E.Horne, P.Odier and S.Joubaud. It has been presented in the European Geosciences Union General Assembly 2016.

Ce travail a été effectué lors de mon stage de master 2 au laboratoire de physique de l’ENS de Lyon sous la direction de E.Horne, P.Odier and S.Joubaud .

Internal waves are produced as a consequence of the dynamic balance between buoyancy and gravity forces when a particle of fluid is vertically displaced in a stable stratified environment. Geophysical systems such as ocean and atmosphere are naturally stratified and therefore suitable for internal waves to propagate. Furthermore, these two environments stock a vast amount of particles in suspension, which present a large spectrum of physical properties (size, density, shape), and can be organic, mineral or pollutant agents. Therefore, it is reasonable to expect that
internal waves will have an active effect over the dynamics of these particles.
In order to study the interaction of internal waves and suspended particles, an idealized experimental setup has been implemented. A linear stratification is produced in a 80×40×17 cm3 tank, in which two dimensional plane waves are created thanks to the innovative wave generator GOAL. In addition, a particle injector has been developed to produce a vertical column of particles within the fluid, displaying the same two-dimensional symmetry as the waves. The particle injector allows to control the volumic fraction of particles and the size of the column.
The presence of internal waves passing through the column of particles allowed to observe two main effects : The column oscillates around an equilibrium position (which is observed in both, the contours an the interior of the column), and the column is displaced as a whole. The column is displaced depending on the characteristics of the
column, the gradient of the density, and the intensity and frequency of the wave.
When displaced, the particles within the column are sucked towards the source of waves. The direction of the displacement of the column is explained by computing the effect of the Lagrangian drift generated by the wave over the time the particles stay in the wave beam before settling.