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In this paper we review the experimental progress that has been made in the study of the evolution of turbulence in low Prandtl number fluids confined by cylindrical containers and heated from below. Heat transport measurements habe revealed that the evolution and nature of non-periodic (i.e., thrbulent) states depend upon the aspect ratio Γ. For large Γ, the fluid flow is non-periodic for Rayleigh numbers R ≥ Rt, with Rt at most a few percent larger than the critical Rayleigh number Rc for the Rayleigh-Bénard instability. In that case the mean amplitude of the non-periodic contribution extrapolates to zero at Rc. For R > Rt, the power is centered about zero frequency. For intermediate aspect ratios (Γ ≅ 5), Rt ≅ 2Rc and at Rt the non-periodically time dependent state has a non-zero amplitude. In this case there is also evidence for the oscillatory instability (OI) of Clever and Busse when R > Rp; but Rp > Rt and the spectral features associated with the OI are broadened. For small aspect ratios (Γ ≅ 2), Rt is increased dramatically, and a quasi-harmonic state evolves for Rp < R < Rt. Above Rt, the power of the non-periodic state is concentrated near finite frequencies.
Ahlers et al. (Sun,) studied this question.