Mixing in weakly turbulent stably stratified flows
Résumé
We analyse mixing in three weakly turbulent stably stratified flows, namely low amplitude breaking internal gravity waves, stably stratified homogeneous decaying turbulence and a stably stratified unstable shear layer. We use the method proposed by Winter et al. [J. Fluid Mech. 289 (1995) 115], which provides an exact expression of the diffusive flux of density responsible for mixing. When the three flows have stabilized and organized into quasi-horizontal layers, we show that the diffusion coefficient behaves linearly as a function of a dynamical parameter that characterizes the largest scales of the flow (a Froude number squared or the inverse of a Richardson number) and we provide a simple expression of this linear law.
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