Large-scale thermal motions of turbulent Rayleigh–Bénard convection in a wide aspect-ratio cylindrical domain

Sakievich, Philip; Peet, Yulia; Adrian, Ronald J.

doi:10.1016/j.ijheatfluidflow.2016.04.011

Cited by 32 publications

(61 citation statements)

References 23 publications

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“…Adrian et al (2017) show that in the case of moderate and large Γ RBC in cylindrical domains there are multiple states that have the potential for super-coherency and that some of these states can be identified by the symmetries of the domain and the boundary conditions. For example, in our previous work (Sakievich et al 2016) a large, long-lived updraft was observed in the central region of the cylinder, and this updraft biased the statistics in an otherwise stationary system. This updraft could just as likely have been a downdraft in another realization of the flow, just as an evenly balanced coin has equal probability of landing on heads or tails over a sufficient number of samples.…”

Section: The Mean Fieldmentioning

confidence: 81%

“…For post-processing, each snapshot is projected onto cylindrical coordinates using spectral interpolation routines native to Nek5000, and the velocity components are transformed from Cartesian to cylindrical. This was previously done on a smaller scale (Sakievich et al 2016), but in this work the transformation has been extended to the entire domain. Cylindrical coordinates are the logical choice for analysing the current dataset and facilitate operations along the domain's periodic, azimuthal direction.…”

Section: Methodsmentioning

confidence: 99%

“…. Temporal filtering removes the majority of the small-scale structures leaving the highly correlated large-scale structures clearly visible, and it is a good technique for observing the slowly evolving large-scale dynamics (Sakievich et al 2016). The temperature field's spectrum is selected for comparison because it contains the most distinguished peak in figure 3.…”

Section: Global Description Of the Large-scale Structurementioning

confidence: 99%

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Temporal dynamics of large-scale structures for turbulent Rayleigh–Bénard convection in a moderate aspect-ratio cylinder

2020

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Section: The Mean Fieldmentioning

confidence: 81%

Section: Methodsmentioning

confidence: 99%

Section: Global Description Of the Large-scale Structurementioning

confidence: 99%

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Temporal dynamics of large-scale structures for turbulent Rayleigh–Bénard convection in a moderate aspect-ratio cylinder

2020

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“…Silano et al [54] numerically studied the Nusselt number for a wide range of Prandtl number (P r = 10 −1 -10 4 ) and reported that the Nusselt number exponent is close to 2/7 for P r = 1 and 0.31 for P r = 10 3 . Sakievich et al [55] performed the direct numerical simulation in a cylinder container of aspect-ratio 6.3 for P r = 6.7 and reported a coherent structure also known as the mean-wind in the turbulent regime.…”

Section: Introductionmentioning

confidence: 99%

Scalings of heat transport and energy spectra of turbulent Rayleigh-Bénard convection in a large-aspect-ratio box

Eswaran

Mishra

2017

International Journal of Heat and Fluid Flow

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Direct Numerical Simulations of turbulent convection in a large aspect-ratio box are carried out in the range of Rayleigh number 7 × 10 4 ≤ Ra ≤ 2 × 10 6 at Prandtl number Pr =0.71. A strong correlation between the vertical velocity and temperature is observed in the turbulent regime at almost all the length scales. Frequency spectra of all the velocities and temperature show a −5/3 law for a wide band of frequencies. The variances of horizontal velocities at different points in the flow yield a single power-law. Probability density functions of velocities and temperature are close to Gaussian only at higher Rayleigh numbers. The mean and variance of temperature clearly show boundary layers, surface layers and a near-homogeneous bulk region. The boundary layer thickness decreases and bulk-homogeneity is enhanced on increasing the Rayleigh numbers. The wave number spectra of the turbulent kinetic energy exhibit kolmogorov like (E(k) ∼ k −5/3 ) and Bolginao-Obukhov like (E(k) ∼ k −11/5 ) behaviour respectively in the central and near-wall regions of the container. An approximate balance between the production due to buoyancy and the dissipation is found in the turbulent kinetic energy budget. Taylor's approximate equation of the production due to turbulent stretching and the dissipation of turbulent enstrophy is modified by the inclusion of buoyancy production in the enstrophy budget. The present results support the previously proposed 2/7 power-law dependence of the average Nusselt number on the Rayleigh number by yielding an exponent

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“…Very large flow patterns have, for example, been observed in moist convection simulations [23][24][25], high Ra number non-penetrative convection [26], and in plane Couette [27,28] at low Re. For RB convection just above the onset of convection, experiments [29][30][31][32][33][34][35] and simulations in large periodic [36][37][38][39] and in very large aspect cylindrical [40][41][42][43][44][45][46] domains have revealed beautiful flow patterns [47][48][49]. Correlations between single point measurements [31,35] and PIV measurements at high Ra [32] have shown a transition between a single and multi-roll structure when Γ exceeds roughly 4, while simulations at Γ = 6.3 and Ra = 9.6 × 10 7 [46] show that large regions of warm rising and cold sinking fluid are still present.…”

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confidence: 99%

Turbulent thermal superstructures in Rayleigh-Bénard convection

et al. 2018

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We report the observation of superstructures, i.e. very large-scale and long living coherent structures in highly turbulent Rayleigh-Bénard convection up to Rayleigh Ra = 10 9 . We perform direct numerical simulations in horizontally periodic domains with aspect ratios up to Γ = 128. In the considered Ra number regime the thermal superstructures have a horizontal extend of six to seven times the height of the domain and their size is independent of Ra. Many laboratory experiments and numerical simulations have focused on small aspect ratio cells in order to achieve the highest possible Ra. However, here we show that for very high Ra integral quantities such as the Nusselt number and volume averaged Reynolds number only converge to the large aspect ratio limit around Γ ≈ 4, while horizontally averaged statistics such as standard deviation and kurtosis converge around Γ ≈ 8, and the integral scale converges around Γ ≈ 32, and the peak position of the temperature variance and turbulent kinetic energy spectra only around Γ ≈ 64.

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Large-scale thermal motions of turbulent Rayleigh–Bénard convection in a wide aspect-ratio cylindrical domain

Cited by 32 publications

References 23 publications

Temporal dynamics of large-scale structures for turbulent Rayleigh–Bénard convection in a moderate aspect-ratio cylinder

Temporal dynamics of large-scale structures for turbulent Rayleigh–Bénard convection in a moderate aspect-ratio cylinder

Scalings of heat transport and energy spectra of turbulent Rayleigh-Bénard convection in a large-aspect-ratio box

Turbulent thermal superstructures in Rayleigh-Bénard convection

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