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Experimental observation of density fluctuations in a stably stratified turbulent fluid

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Using planar laser induced fluorescence, we present quantitative measurements of density fluctuations in a two-layer stably stratified fluid forced by an oscillating grid located at the bottom of the tank. The turbulence produced by the grid spreads rapidly in the lower layer and is blocked at the interface between the dense and and the light fluid. The interface height increases then slowly by entraining some of the fluid of the upper layer in the turbulent layer. We propose a new method to separate the "wave" part from the "turbulent" part of the density fluctuations. We then discuss the role of these density fluctuations in the dynamics of the mixed layer depth.

Author(s):

antoine venaille    
ENS de Lyon, CNRS
France

Louis Gostiaux    
LMFA, école Centrale Lyon, CNRS
France

Joël Sommeria    
LEGI (Grenoble), CNRS
France