Similarities between characteristics of convective turbulence in confined and extended domains

Abstract

To understand turbulent convection at very high Rayleigh numbers typical of natural phenomena, computational studies in slender cells are an option if the needed resources have to be optimized within available limits. However, the accompanying horizontal confinement affects some properties of the flow. Here, we explore the characteristics of turbulent fluctuations in the velocity and temperature fields in a cylindrical convection cell of aspect ratio 0.1 by varying the Prandtl number $Pr$ between 0.1 and 200 at a fixed Rayleigh number $Ra=3\times 10^{10}$, and find that the fluctuations weaken with increasing $Pr$, quantitatively as in aspect ratio 25. The probability density function (PDF) of temperature fluctuations in the bulk region of the slender cell remains mostly Gaussian, but increasing departures occur as $Pr$ increases beyond unity. We assess the intermittency of the velocity field by computing the PDFs of velocity derivatives and of the kinetic energy dissipation rate, and find increasing intermittency as $Pr$ decreases. In the bulk region of convection, a common result applicable to the slender cell, large aspect ratio cells, as well as in 2D convection, is that the turbulent Prandtl number decreases as $P{r}^{-1/3}$.

13 pages, 16 figures

References in corpus (9)

• Scaling of large-scale quantities in Rayleigh-Bénard convection
• Global and local statistics in turbulent convection at low Prandtl numbers
• Elliptical Instability and Multi-Roll Flow Modes of the Large-scale Circulation in Confined Turbulent Rayleigh-Bénard Convection
• Collapse of Coherent Large Scale Flow in Strongly Turbulent Liquid Metal Convection
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• Prandtl number dependence of the small-scale properties in turbulent Rayleigh-Bénard convection
• Non-Boussinesq convection at low Prandtl numbers relevant to the Sun
• Convective heat transport in slender cells is close to that in wider cells at high Rayleigh and Prandtl numbers
• Extreme dissipation event due to plume collision in a turbulent convection cell

Cited by in corpus (8)

• Lorentz force mediation of turbulent dynamo transitions
• Turbulent mesoscale convection in the Boussinesq limit and beyond
• Turbulent Prandtl number from isotropically forced turbulence
• Transient and steady convection in two dimensions
• Turbulent convection in rotating slender cells
• Collective variables between large-scale states in turbulent convection
• Scale-resolved turbulent Prandtl number for Rayleigh-Bénard convection at $\mathbf{Pr}=10^{-3}$
• Influence of plume activity on thermal convection in a rectangular cell