On Lagrangian and Eulerian Acceleration Statistics in Turbulent Stratified Shear Flows

2 Avril à 11h00 (locaux M2P2 Château Gombert)
Séminaire M2P2

Frank G. Jacobitz, Kai Schneider, and Marie Farge

Résumé: The Lagrangian and Eulerian acceleration statistics in homogeneous turbulence with uniform shear and stratification are studied using direct numerical simulations. The Richardson number is varied from Ri = 0, corresponding to unstratified shear flow, to Ri = 1, corresponding to strongly stratified shear flow. The probability density functions (pdfs) of both Lagrangian and Eulerian accelerations show a strong and similar influence on the Richardson number and extreme values for Eulerian acceleration are stronger than those observed for the Lagrangian acceleration.
Similarly, the Eulerian time-rate of change of fluctuating density is observed to have larger extreme values than that of the Lagrangian time-rate of change. Hence, the time-rate of change of fluctuating density obtained at a fixed location by an Eulerian observer is mainly due to advection of fluctuating density through this location, while the time-rate of change of fluctuating density following a fluid particle is substantially smaller, and due to production and dissipation of fluctuating density.

Le Pr. Frank Jacobitz nous présentera ses travaux, le jeudi 2 avril à 11 heures, dans le petit amphi du M2P2

(Château Gombert IMT La Jetée, 2ème étage)