Near isotropic behaviour of turbulent thermal convection

Abstract

We investigate the anisotropy in turbulent convection in a 3D box using direct numerical simulation. We compute the anisotropic parameter $A=u_{\perp }^2/(2u_{\parallel }^2)$, where $u_{\perp }$ and $u_{\parallel }$ are the components of velocity perpendicular and parallel to the buoyancy direction, the shell and ring spectra, and shell-to-shell energy transfers. We observe that the flow is nearly isotropic for the Prandtl number $\mathrm{Pr}\approx 1$, but the anisotropy increases with the Prandtl number. For $\mathrm{Pr}=\infty$, $A\approx 0.3$, thus anisotropy is not very significant even in extreme cases. We also observe that $u_{\parallel }$ feeds energy to $u_{\perp }$ via pressure. The computation of shell-to-shell energy transfers reveals that the energy transfer in turbulent convection is local and forward, similar to hydrodynamic turbulence. These results are consistent with the Kolmogorov's spectrum observed by Kumar et al.~[Phys. Rev. E {\bf 90}, 023016 (2014)] for turbulent convection.

References in corpus (4)

• Energy Spectrum of Buoyancy-Driven Turbulence
• Anisotropic energy transfers in quasi-static magnetohydrodynamic turbulence
• Anisotropy, inhomogeneity and inertial range scalings in turbulent convection
• On the two-dimensionalization of quasistatic magnetohydrodynamic turbulence

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• Convective mesoscale turbulence at very low Prandtl numbers
• Prandtl number dependence of the small-scale properties in turbulent Rayleigh-Bénard convection
• Lorentz force mediation of turbulent dynamo transitions
• Similarities between the structure functions of thermal convection and hydrodynamic turbulence
• Contrasting turbulence in stably stratified flows and thermal convection
• A revisit of generalized scaling of forced turbulence through flux analysis