Figure 1:
Researchers have explored properties of turbulence in two important situations: (Left) A layer of fluid of thickness d under the influence of gravity g is heated from below, so that the temperature T_{b} is higher than the temperature T_{t} at the top (Rayleigh-Bénard case). When the temperature difference is sufficiently large, a transition from the state of pure heat conduction to a state of convection occurs. He et al.’s experiment [1] focuses on the asymptotic state of highly turbulent convection. (Right) In a Taylor-Couette system, a fluid fills the gap between coaxial cylinders with radii r_{i} and r_{o}, d=r_{o}-r_{i}, which rotate independently with the angular velocities Ω_{i} and Ω_{o}, respectively. At high enough rotation differential, Ω_{i}-Ω_{o}>0, a transition from the purely cylindrical flow to axially symmetric Taylor vortices occurs. The latter become turbulent at much higher values of Ω_{i}-Ω_{o}, which is the regime investigated in Huisman et al.’s experiment [2].