On the centrifugal effect in turbulent rotating thermal convection: onset and heat transport

Abstract

The effect of centrifugal force in turbulent rotating Rayleigh–Bénard convection (RRBC) is studied experimentally in an aspect-ratio $\varGamma =1$ cylindrical convection cell and in the ranges of the Froude number $0.004\leq Fr \leq 0.363$ and the Rayleigh number $2.8\times 10^8 \leq Ra \leq 9.5\times 10^9$ , and with the Prandtl number fixed at $Pr=4.34$ . We use the bulk temperature anomaly to determine the onset Froude number $Fr_c$ , beyond which the centrifugal effects cannot be regarded as insignificant. It is found that $Fr_c$ depends on $Ra$ as $Fr_c\sim Ra^{0.53}$ , which may be understood qualitatively by the idea of local force balance. For $Fr>Fr_c$ , the centrifugal effect is more pronounced for smaller $Ra$ , which is also found for larger constant $1/Ro$ . This implies that the response of the system to the centrifugal force depends on the flow states, which, in RRBC, is mainly determined by the competition between the buoyancy and Coriolis forces. Detailed analysis of the sidewall temperature signal shows results consistent with those obtained from the bulk temperature. Based on the above results, we propose a different division of the $1/Ro$ – $Fr$ phase space than previously suggested. For the heat transport, the results under fixed $1/Ro$ show well-defined $Nu$ – $Ra$ scalings, which can provide a better prediction for the heat transport when extrapolating to the unexplored regions in the phase space.

An experimental study of off-centred rotating thermal convection: a laboratory model for the tidal effects

“…, which is consistent with the finding from a previous study at (Hu et al. 2022). With this baseline, we can define to study the offset effects, as shown in figure 6( a ).…”

“…This is verified by a direct measurement in a recent RRBC experiment, which further shows that the onset value depends on as (Hu et al. 2022). Here, it is worth pointing out that the onset Froude number may have important implications for the conventional RRBC experiments.…”

“…The structure of the rotating table has been described in detail in Hu et al. (2022). Here, only the key features and the differences with the centred experiments are introduced.…”

“…The centrifugal force tends to generate accumulations of hot fluid parcels at the cell centre and cold ones around the sidewall. After the centrifugal effect sets in, the flow states can be divided into a weak- and a strong-centrifugal regime (Hu, Xie & Xia 2022). In the weak-centrifugal regime, the radial diffusive motions of hot and cold columns are enhanced (Noto et al.…”

Planetary Core‐Style Rotating Convective Flows in Paraboloidal Laboratory Experiments

“…This value provides an upper bounding Rossby number estimate since the centrifugal free fall velocity is used in constructing Ro ⊥ . Centrifugal free fall is accurate when the top and bottom bounding surfaces are planar (Hu et al., 2022; Jiang et al., 2020). When either of these surfaces are nonplanar and Ro ⊥ ≪ 1, topographic vortex stretching will act to limit the centrifugal velocity to smaller thermal wind speeds (e.g., Aubert et al., 2001; Aurnou et al., 2020).…”