“…Examples of such structures plumes in Rayleigh-Bérnard convection [72], structures behind a splitter plate [73], and large vortical structures in two-dimensional or stratified flows [1,35,36]. In three-dimensional flows, as we will see in greater detail below, energy that is pumped into the flow at the injection scale L cascades, as first suggested by Richardson [55], from large-scale eddies to small-scale ones till it is eventually dissipated around and beyond the dissipation scale η d . By contrast, two-dimensional turbulence [35,36,74,75] displays a dual cascade: there is an inverse cascade of energy from the scale at which it is pumped into the system to large length scales and a direct cascade of enstrophy Ω = 1 2 ω 2 to small length scales.…”