Experimental Evidence for the Existence of the Ultimate Regime in Rapidly Rotating Turbulent Thermal Convection

Jiang, Hechuan; Wang, Dongpu; Liu, Shuang; Sun, Chao

doi:10.1103/physrevlett.129.204502

Cited by 10 publications

(16 citation statements)

References 77 publications

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“…In the present study, we consider the coupling effect of shear and buoyancy on the flow structure and heat and momentum transfer, that is, (Nu h , Nu ω ) = f (Ra, Ω). Therefore, referring to the results of our previous experiments and simulations of ACRBC (Jiang et al 2020(Jiang et al , 2022Wang et al 2022b), Pr = 4.3 is taken for water at 40 • C, and η is set to be 0.5. Considering the Boussinesq approximation, αΔ 1 is required.…”

Section: Other Numerical Detailsmentioning

confidence: 99%

“…Considering the Boussinesq approximation, αΔ 1 is required. According to (2.2), we choose αΔ = 6.67 × 10 −3 and then Ro −1 = 20, which is also in the parameter range of our previous experiments, corresponding to a temperature difference Δ ≈ 17.3 K for water (Jiang et al 2020(Jiang et al , 2022. The non-Oberbeck-Boussinesq effect is not obvious at this temperature difference (Ahlers et al 2006), and the Oberbeck-Boussinesq conditions are well satisfied.…”

Section: Other Numerical Detailsmentioning

confidence: 99%

“…As the buoyancy is perpendicular to the cylinder surface, the aspect ratio (here, the aspect ratio is defined as the ratio of circumference to the gap length) in ACRBC is larger than that in RB convection. Recent studies show that the ACRBC owns scaling laws similar to those of classical RB convection, and is an efficient way to reach the ultimate regime (Jiang et al 2020(Jiang et al , 2022. The angular velocity difference between the inner and outer cylinders offers shear for the system, therefore the system can also be regarded as a TC system with radial temperature difference.…”

Section: Introductionmentioning

confidence: 98%

See 2 more Smart Citations

From sheared annular centrifugal Rayleigh–Bénard convection to radially heated Taylor–Couette flow: exploring the impact of buoyancy and shear on heat transfer and flow structure

Zhong,

Wang,

Sun

2023

J. Fluid Mech.

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We investigate the coupling effect of buoyancy and shear based on an annular centrifugal Rayleigh–Bénard convection (ACRBC) system in which two cylinders rotate with an angular velocity difference. Direct numerical simulations are performed in a Rayleigh number range $10^6\leq Ra\leq 10^8$ , at fixed Prandtl number $Pr=4.3$ , inverse Rossby number $Ro^{-1}=20$ , and radius ratio $\eta =0.5$ . The shear, represented by the non-dimensional rotational speed difference $\varOmega$ , varies from $0$ to $10$ , corresponding to an ACRBC without shear and a radially heated Taylor–Couette flow with only the inner cylinder rotating, respectively. A stable regime is found in the middle part of the interval for $\varOmega$ , and divides the whole parameter space into three regimes: buoyancy-dominated, stable and shear-dominated. Clear boundaries between the regimes are given by linear stability analysis, meaning the marginal state of the flow. In the buoyancy-dominated regime, the flow is a quasi-two-dimensional flow on the $r\varphi$ plane; as shear increases, both the growth rate of instability and the heat transfer are depressed. In the shear-dominated regime, the flow is mainly on the $rz$ plane. The shear is so strong that the temperature acts as a passive scalar, and the heat transfer is greatly enhanced. The study shows that shear can stabilize buoyancy-driven convection, makes a detailed analysis of the flow characteristics in different regimes, and reveals the complex coupling mechanism of shear and buoyancy, which may have implications for fundamental studies and industrial designs.

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Section: Other Numerical Detailsmentioning

confidence: 99%

Section: Other Numerical Detailsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

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From sheared annular centrifugal Rayleigh–Bénard convection to radially heated Taylor–Couette flow: exploring the impact of buoyancy and shear on heat transfer and flow structure

Zhong,

Wang,

Sun

2023

J. Fluid Mech.

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“…Experimental or numerical observations of the (asymptotic) ultimate regime prove to be very difficult, and no final consensus has been reached so far about its existence in a pure RB setting (Doering & Constantin 1996;Chavanne et al 1997;Zhu et al 2018Zhu et al , 2019aUrban et al 2019;Roche 2020) (see Ahlers et al (2009) for a less recent but more synthetic review). When the gravity is artificially increased using centrifugal force, one can indeed observe hints of an ultimate regime (Jiang et al 2022). On the other hand, various modifications of the RB geometry aiming at modifying the influence of the boundary layers result in experimental observation of a regime where Nu ∼ Ra 1/2 : using highly elongated cells (Pawar & Arakeri 2016;Castaing et al 2017), using rough (Ciliberto & Laroche 1999;Rusaouën et al 2018;Zhu et al 2019b;Kawano et al 2021) or porous (Zou & Yang 2021;Motoki, Kawahara & Shimizu 2022) boundaries, or radiatively heating the flow (Lepot, Aumaître & Gallet 2018;Bouillaut et al 2019).…”

Section: Introductionmentioning

confidence: 99%

“…When the gravity is artificially increased using centrifugal force, one can indeed observe hints of an ultimate regime (Jiang et al. 2022). On the other hand, various modifications of the RB geometry aiming at modifying the influence of the boundary layers result in experimental observation of a regime where : using highly elongated cells (Pawar & Arakeri 2016; Castaing et al.…”

Section: Introductionmentioning

confidence: 99%

Asymptotic ultimate regime of homogeneous Rayleigh–Bénard convection on logarithmic lattices

Barral

Dubrulle

2023

J. Fluid Mech.

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We investigate how the heat flux $Nu$ scales with the imposed temperature gradient $Ra$ in homogeneous Rayleigh–Bénard convection using one-, two- and three-dimensional simulations on logarithmic lattices. Logarithmic lattices are a new spectral decimation framework which enables us to span an unprecedented range of parameters ( $Ra$ , $Re$ , $\Pr$ ) and test existing theories using little computational power. We first show that known diverging solutions can be suppressed with a large-scale friction. In the turbulent regime, for $\Pr \approx 1$ , the heat flux becomes independent of viscous processes (‘asymptotic ultimate regime’, $Nu\sim Ra ^{1/2}$ with no logarithmic correction). We recover scalings coherent with the theory developed by Grossmann and Lohse, for all situations where the large-scale frictions keep a constant magnitude with respect to viscous and diffusive dissipation. We also identify another turbulent friction-dominated regime at $\Pr \ll 1$ , where deviations from the Grossmann and Lohse prediction are observed. These two friction-dominated regimes may be relevant in some geophysical or astrophysical situations, where large-scale friction arises due to rotation, stratification or magnetic field.

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Temperature fluctuations and heat transport in partitioned supergravitational thermal turbulence

Wang,

Liu,

Lai

et al. 2024

Acta Mech. Sin.

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Experimental Evidence for the Existence of the Ultimate Regime in Rapidly Rotating Turbulent Thermal Convection

Cited by 10 publications

References 77 publications

From sheared annular centrifugal Rayleigh–Bénard convection to radially heated Taylor–Couette flow: exploring the impact of buoyancy and shear on heat transfer and flow structure

From sheared annular centrifugal Rayleigh–Bénard convection to radially heated Taylor–Couette flow: exploring the impact of buoyancy and shear on heat transfer and flow structure

Asymptotic ultimate regime of homogeneous Rayleigh–Bénard convection on logarithmic lattices

Temperature fluctuations and heat transport in partitioned supergravitational thermal turbulence

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