Abstract
We report results on rotating stratified turbulence in the absence of forcing, with large-scale isotropic initial conditions,
using direct numerical simulations computed on grids of up to $4096^3$ points. The Reynolds and Froude numbers are respectively
equal to $Re=5.4\times 10^4$ and $Fr=0.0242$. The ratio of the Brunt-V\"ais\"al\"a to the inertial wave frequency, $N/f$, is
taken to be equal to 5, a choice appropriate to model the dynamics of the southern abyssal ocean at mid latitudes. This gives a global
buoyancy Reynolds number $R_B=ReFr^2=32$, a value sufficient for some isotropy to be recovered in the small scales beyond the
Ozmidov scale, but still moderate enough that the intermediate scales where waves are prevalent are well resolved. We concentrate
on the large-scale dynamics and confirm that the Froude number based on a typical vertical length scale is of order unity, with
strong gradients in the vertical. Two characteristic scales emerge from this computation, and are identified from sharp variations
in the spectral distribution of either total energy or helicity. A spectral break is also observed at a scale at which the partition of
energy between the kinetic and potential modes changes abruptly, and beyond which a Kolmogorov-like spectrum recovers. Large slanted
layers are ubiquitous in the flow in the velocity and temperature fields, and a large-scale enhancement of energy is also observed,
directly attributable to the effect of rotation.