Dispersion of Lagrangian particles by waves and eddies in turbulent flows

P.D. MININNI

Paris

Workshop; Wave interactions and turbulence; 2018

Ecole Polytechnique

In this talk I will present several results on the effect of different forcing functions and of the local gradient Richardson number Rigon the vertical and horizontal mixing of Lagrangian tracers in stably stratified turbulence under the Boussinesqapproximation, and present a wave and continuous-time random walk model for single- and two-particle vertical dispersion. The model consists of a random superposition of linear waves withtheir amplitude based on the observed Lagrangian spectrum of vertical velocity, and a random walkprocess to capture overturning that depends on the statistics of Rig among other Eulerian quantities.The model is in good agreement with direct numerical simulations of stratified turbulence, wheresingle- and two-particle dispersion differs from the homogeneous and isotropic case. Moreover, themodel gives insight into the mixture of linear and non-linear physics in the problem, as well as onthe different processes responsible for vertical turbulent dispersion.