### Abstract

We present measurements of the azimuthal rotation velocity $\dot{{\it\theta}}(t)$θ˙(t) and thermal amplitude ${\it\delta}(t)$δ(t) of the large-scale circulation in turbulent Rayleigh–Bénard convection with modulated rotation. Both $\dot{{\it\theta}}(t)$θ˙(t) and ${\it\delta}(t)$δ(t) exhibit clear oscillations at the modulation frequency ${\it\omega}$ω. Fluid acceleration driven by oscillating Coriolis force causes an increasing phase lag in $\dot{{\it\theta}}(t)$θ˙(t) when ${\it\omega}$ω increases. The applied modulation produces oscillatory boundary layers and the resulting time-varying viscous drag modifies ${\it\delta}(t)$δ(t) periodically. Oscillation of $\dot{{\it\theta}}(t)$θ˙(t) with maximum amplitude occurs at a finite modulation frequency ${\it\omega}^{\ast }$ω∗. Such a resonance-like phenomenon is interpreted as a result of optimal coupling of ${\it\delta}(t)$δ(t) to the modulated rotation velocity. We show that an extended large-scale circulation model with a relaxation time for ${\it\delta}(t)$δ(t) in response to the modulated rotation provides predictions in close agreement with the experimental results.

Original language | English |
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Pages (from-to) | R4- |

Number of pages | 12 |

Journal | Journal of fluid mechanics |

Volume | 778 |

DOIs | |

Publication status | Published - 7 Aug 2015 |

### Keywords

- METIS-311083
- IR-97385

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## Cite this

Zhong, J. Q., Sterl, S. H., & Li, H. M. (2015). Dynamics of the large-scale circulation in turbulent Rayleigh–Bénard convection with modulated rotation.

*Journal of fluid mechanics*,*778*, R4-. https://doi.org/10.1017/jfm.2015.400