Flow reversals in thermally driven turbulence
Abstract
We analyze the reversals of the large scale flow in Rayleigh-B\'enard convection both through particle image velocimetry flow visualization and direct numerical simulations (DNS) of the underlying Boussinesq equations in a (quasi) two-dimensional, rectangular geometry of aspect ratio 1. For medium Prandtl number there is a diagonal large scale convection roll and two smaller secondary rolls in the two remaining corners diagonally opposing each other. These corner flow rolls play a crucial role for the large scale wind reversal: They grow in kinetic energy and thus also in size thanks to plume detachments from the boundary layers up to the time that they take over the main, large scale diagonal flow, thus leading to reversal. Based on this mechanism we identify a typical time scale for the reversals. We map out the Rayleigh number vs Prandtl number phase space and find that the occurrence of reversals very sensitively depends on these parameters.
Cite
@article{arxiv.1109.6868,
title = {Flow reversals in thermally driven turbulence},
author = {Kazuyasu Sugiyama and Rui Ni and Richard J. A. M. Stevens and Tak Shing Chan and Sheng-Qi Zhou and Heng-Dong Xi and Chao Sun and Siegfried Grossmann and Ke-Qing Xia and Detlef Lohse},
journal= {arXiv preprint arXiv:1109.6868},
year = {2011}
}
Comments
4 pages, 4 figures