Plume Motion and Large-Scale Circulation in a Cylindrical Rayleigh-Bénard Cell

Abstract

We used the time correlation of shadowgraph images to determine the angle $Theta$ of the horizontal component of the plume velocity above (below) the center of the bottom (top) plate of a cylindrical Rayleigh-B'enard cell of aspect ratio $Gamma equiv D/L = 1$ ($D$ is the diameter and $L simeq 87$ mm the height) in the Rayleigh-number range $7 imes 10^7 leq R leq 3 imes 10^{9}$ for a Prandtl number $sigma = 6$. We expect that $Theta$ gives the direction of the large-scale circulation. It oscillates time-periodically. Near the top and bottom plates $Theta(t)$ has the same frequency but is anti-correlated.Comment: 4 pages, 6 figure