Single-particle Lagrangian statistics from direct numerical simulations of rotating-stratified turbulence

Using direct numerical simulations of forced Boussinesq equations, we study the influence of these effects on the motion of fluid particles. We perform a detailed study of Lagrangian statistics of acceleration, velocity, and related quantities, focusing on cases where the frequencies associated with rotation and stratification (RaS), f and N, respectively, are held at a fixed ratio N/f = 5.

The simulations are performed in a periodic domain, at Reynolds number Re approximate to 4000, and Froude number Fr in the range 0.03 less than or similar to Fr less than or similar to 0.2 (with Rossby number Ro = 5Fr). As the intensity of RaS increases, a sharp transition is observed between a regime dominated by eddies to a regime dominated by waves, which corresponds to Fr less than or similar to 0.07. For the given runs, this transition to a wave-dominated regime can also be seemingly described by simply comparing the timescales 1/N and tau(eta), the latter being the Kolmogorov timescale based on the mean kinetic energy dissipation.