APS/Carin Cain

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 $Tb$ is higher than the temperature $Tt$ 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 $ri$ and $ro$, $d=ro-ri$, which rotate independently with the angular velocities $Ωi$ and $Ωo$, respectively. At high enough rotation differential, $Ωi-Ωo>0$, a transition from the purely cylindrical flow to axially symmetric Taylor vortices occurs. The latter become turbulent at much higher values of $Ωi-Ωo$, which is the regime investigated in Huisman et al.’s experiment [2].