Upward and downward transfer of energy in rotating stratified flows

We investigate experimentally and numerically the evolution of forced turbulence in the strongly stratified regime and for rotation rates covering the regimes associated to a direct and an inverse energy cascade. The experiments are performed by means of a rotating table with a diameter of 2 m. The energy is injected by periodically creating columnar dipoles. Direct numerical simulations (DNS) complement the experiments in order to reach higher Reynolds numbers. The turbulence exhibits pancake structures with a large horizontal scale and a vertical thickness increasing with the rotation rate. For strong enough rotating rates, horizontal scales larger than the forcing scales appear in the experiments consistently with the observation of an inverse cascade in the DNS. We have found that the critical Rossby number below which the inverse cascade appears depends on the horizontal Froude number $F_h$.