Near isotropic behavior of turbulent thermal convection

Dinesh Nath, Ambrish Pandey, Abhishek Kumar, Mahendra K. Verma

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    Abstract

    We investigate the anisotropy in turbulent convection in a 3D box using direct numerical simulation. We compute the anisotropic parameter A=u2⊥/(2u2∥), where u⊥ and u∥ 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 Pr≈1, but the anisotropy increases with the Prandtl number. For Pr=∞, A≈0.3, thus anisotropy is not very significant even in extreme cases. We also observe that u∥ feeds energy to u⊥ 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.
    Original languageEnglish
    Article number064302
    Number of pages27
    JournalPhys. Rev. Fluids
    Volume1
    DOIs
    Publication statusPublished - 28 Oct 2016

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