Frequency spectra of turbulent thermal convection with uniform rotation

Abstract

The frequency spectra of the entropy and kinetic energy along with the power spectrum of the thermal flux are computed from direct numerical simulations for turbulent Rayleigh-Bénard convection with uniform rotation about a vertical axis in low-Prandtl-number fluids ($\mathrm{Pr} < 0.6$). Simulations are done for convective Rossby numbers $\mathrm{Ro} \ge 0.2$. The temporal fluctuations of these global quantities show two scaling regimes: (i) $ω^{-2}$ at higher frequencies for all values of $\mathrm{Ro}$ and (ii) $ω^{-γ_1}$ at intermediate frequencies with $γ_1 \approx 4$ for $\mathrm{Ro} > 1$, while $4 < γ_1 < 6.6$ for $0.2 \le \mathrm{Ro} < 1$.