TY - JOUR

T1 - Similarities between characteristics of convective turbulence in confined and extended domains

AU - Pandey, Ambrish

AU - Krasnov, Dmitry

AU - Schumacher, Jörg

AU - Samtaney, Ravi

AU - Sreenivasan, Katepalli R.

N1 - Publisher Copyright:
© 2022 Elsevier B.V.

PY - 2022/12/15

Y1 - 2022/12/15

N2 - 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=3×1010, 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 Pr−1/3.

AB - 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=3×1010, 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 Pr−1/3.

KW - Aspect ratio dependence

KW - Convection at variable Prandtl numbers

KW - High Rayleigh number convection

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U2 - 10.1016/j.physd.2022.133537

DO - 10.1016/j.physd.2022.133537

M3 - Review article

AN - SCOPUS:85140063712

SN - 0167-2789

VL - 442

JO - Physica D: Nonlinear Phenomena

JF - Physica D: Nonlinear Phenomena

M1 - 133537

ER -