Evolution of Turbulence from the Rayleigh-Bénard Instability

Measurements of heat transport through horizontal layers of fluid heated from below are reported for three aspect ratios (=D2d, D=diameter, d=heightofthecylindricalcells). They show that for =57 the fluid flow is turbulent, in the sense that it has an a nonperiodic time dependence, for numbers R>Rₓ with RₓR₂ (R₂) is the critical R for onset of fluid flow). For =4. 72, we find Rₓ2R₂. For =2. 08, a quasiperiodic state exists for R₏<~R<~Rₓ, with R₏10R₂ and Rₓ11R₂.