research10.1017/jfm.2015.316

# Large-scale mean patterns in turbulent convection

## Abstract

Large-scale patterns, which are well-known from the spiral defect chaos regime of thermal convection at Rayleigh numbers \$Ra < 10^4\$, continue to exist in three-dimensional numerical simulations of turbulent Rayleigh-B\'{e}nard convection in extended cylindrical cells with an aspect ratio \$\Gamma=50\$ and \$Ra>10^5\$. They are uncovered when the turbulent fields are averaged in time and turbulent fluctuations are thus removed. We apply the Boussinesq closure to estimate turbulent viscosities and diffusivities, respectively. The resulting turbulent Rayleigh number \$Ra_{\ast}\$, that describes the convection of the mean patterns, is indeed in the spiral defect chaos range. The turbulent Prandtl numbers are smaller than one with \$0.2\le Pr_{\ast}\le 0.4\$ for Prandtl numbers \$0.7 \le Pr\le 10\$. Finally, we demonstrate that these mean flow patterns are robust to an additional finite-amplitude side wall-forcing when the level of turbulent fluctuations in the flow is sufficiently high.Comment: 13 pages, 7 figure

## Similar works

This paper was published in arXiv.org e-Print Archive.

# Having an issue?

Is data on this page outdated, violates copyrights or anything else? Report the problem now and we will take corresponding actions after reviewing your request.