Frequency spectra of turbulent thermal convection with uniform rotation

TL;DR

This study investigates the frequency spectra of entropy, kinetic energy, and thermal flux in turbulent rotating Rayleigh-Bénard convection through direct numerical simulations, revealing distinct scaling regimes at different frequencies and rotation rates.

Contribution

The paper provides new insights into the spectral behavior of turbulent convection under rotation, highlighting two distinct scaling regimes and their dependence on the convective Rossby number.

Findings

Frequency spectra exhibit a 2 power-law decay at high frequencies.

Intermediate frequency scaling varies with Rossby number, with 4 for  > 1.

Scaling exponents range from 4 to 6.6 for 0.2   1.

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-B\'{e}nard 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) $\omega^{-2}$ at higher frequencies for all values of $\mathrm{Ro}$ and (ii) $\omega^{-\gamma_1}$ at intermediate frequencies with $\gamma_1 \approx 4$ for $\mathrm{Ro} > 1$, while $4 < \gamma_1 < 6.6$ for $0.2 \le \mathrm{Ro} < 1$.