Long relaxation times and tilt sensitivity in Rayleigh Bénard turbulence

Chillà, Francesca; Rastello, Marie; Chaumat, Sébastien; Castaing, B.

doi:10.1140/epjb/e2004-00261-3

Cited by 78 publications

(84 citation statements)

References 23 publications

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“…• C, where σ = 4.38, κ = 1.52 × 10 −7 m 2 /s, ν = 6.70 × 10 −7 m 2 /s, α = 3.88 × 10 −4 K −1 , and λ = 0.630 W/m K. We never observed long transients like those reported by Chillà et al(2004b) for Γ = 0.5 (see Brown et al (2005)). On occasion we tilted the apparatus by 2…”

Section: The Datasupporting

confidence: 57%

Heat transport by turbulent Rayleigh–Bénard convection in cylindrical samples with aspect ratio one and larger

et al. 2005

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We present high-precision measurements of the Nusselt number N as a function of the Rayleigh number R for cylindrical samples of water (Prandtl number σ = 4.38) with diameters D = 49.7, 24.8, and 9.2 cm, all with aspect ratio Γ ≡ D/L ≃ 1 (L is the sample height). In addition, we present data for D = 49.7 and Γ = 1.5, 2, 3, and 6. For each sample the data cover a range of a little over a decade of R. For Γ ≃ 1 they jointly span the range 10Where needed, the data were corrected for the influence of the finite conductivity of the top and bottom plates and of the side walls on the heat transport in the fluid to obtain estimates of N ∞ for plates with infinite conductivity and sidewalls of zero conductivity. For Γ ≃ 1 the effective exponent γ ef f of N ∞ = N 0 R γ ef f ranges from 0.28 near R = 10 8 to 0.333 near R ≃ 7 × 10 10 . For R < ∼ 10 10 the results are consistent with the Grossmann-Lohse model. For larger R, where the data indicate that N ∞ (R) ∼ R 1/3 , the theory has a smaller γ ef f than 1/3 and falls below the data. The data for Γ > 1 are only a few percent smaller than the Γ = 1 results.

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Section: The Datasupporting

confidence: 57%

Heat transport by turbulent Rayleigh–Bénard convection in cylindrical samples with aspect ratio one and larger

et al. 2005

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“…Small changes of order of 2% have been also found when tilting the cell in [47,85]. These are evidently consequences of the action of gravity on the large scale flow.…”

Section: Nu-ra Scalingmentioning

confidence: 86%

“…Many experiments at moderate and high Rayleigh numbers have been performed in water because these experiments allow several possibilities of visualization [44][45][46]. The highest Rayleigh numbers reached for convection in water are those of the group in Hong Kong [46] which reached Ra = 5 × 10 12 at P r = 4 and those of the group in Lyon [47,48] in which Ra = 4 × 10 12 at P r = 2 was obtained. The majority of the laboratory experiments are conducted in cylindrical cells; some studies have been performed in rectangular convection cells [49][50][51][52][53][54].…”

Section: Working Fluids and Accessible Parameter Rangesmentioning

confidence: 99%

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New perspectives in turbulent Rayleigh-Bénard convection

2012

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Abstract. Recent experimental, numerical and theoretical advances in turbulent Rayleigh-Bénard convection are presented. Particular emphasis is given to the physics and structure of the thermal and velocity boundary layers which play a key role for the better understanding of the turbulent transport of heat and momentum in convection at high and very high Rayleigh numbers. We also discuss important extensions of Rayleigh-Bénard convection such as non-Oberbeck-Boussinesq effects and convection with phase changes.

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“…We can use a highly simplified model to estimate the order of magnitude of this effect. This model is based on one used successfully to estimate the effect of tilting on the Reynolds number [Chillà et al(2004b), Ahlers et al (2005)]. Tilting the sample by a small angle β relative to gravity results in a buoyancy force per unit area in the thermal boundary layers approximately given by ρlgβα∆T /2 parallel to the plates, where l is the boundary-layer thickness.…”

Section: Tilting the Samplementioning

confidence: 99%

Rotations and cessations of the large-scale circulation in turbulent Rayleigh–Bénard convection

2006

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We present a broad range of measurements of the angular orientation θ 0 (t) of the largescale circulation (LSC) of turbulent Rayleigh-Bénard convection as a function of time. We used two cylindrical samples of different overall sizes, but each with its diameter nearly equal to its height. The fluid was water with a Prandtl number of 4.38. The time series θ 0 (t) consisted of meanderings similar to a diffusive process, but in addition contained large and irregular spontaneous reorientation events through angles ∆θ. We found that reorientations can occur by two distinct mechanisms. One consists of a rotation of the circulation plane without any major reduction of the circulation strength. The other involves a cessation of the circulation, followed by a restart in a randomly chosen new direction. Rotations occurred an order of magnitude more frequently than cessations. Rotations occurred with a monotonically decreasing probability distribution p(∆θ), i.e. there was no dominant value of ∆θ and small ∆θ were more common than large ones. For cessations p(∆θ) was uniform, suggesting that information of θ 0 (t) before the cessation is lost. Both rotations and cessations have Poissonian statistics in time, and can occur at any θ 0 . The average azimuthal rotation rate |θ| increased as the circulation strength of the LSC decreased. Tilting the sample relative to gravity significantly reduced the frequency of occurrence of both rotations and cessations.

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Long relaxation times and tilt sensitivity in Rayleigh Bénard turbulence

Cited by 78 publications

References 23 publications

Heat transport by turbulent Rayleigh–Bénard convection in cylindrical samples with aspect ratio one and larger

Heat transport by turbulent Rayleigh–Bénard convection in cylindrical samples with aspect ratio one and larger

New perspectives in turbulent Rayleigh-Bénard convection

Rotations and cessations of the large-scale circulation in turbulent Rayleigh–Bénard convection

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