Summary: Reorientation of the Large-Scale Circulation in Turbulent Rayleigh-BeŽnard Convection
Eric Brown, Alexei Nikolaenko, and Guenter Ahlers
Department of Physics and iQUEST, University of California, Santa Barbara, California 93106, USA
(Received 18 March 2005; published 18 August 2005)
We present measurements of the orientation 0t of the large-scale circulation (LSC) of turbulent
Rayleigh-BeŽnard convection in cylindrical cells of aspect ratio 1. 0t undergoes irregular reorientations.
It contains reorientation events by rotation through angles with a monotonically decreasing probability
distribution p, and by cessations (where the LSC stops temporarily) with a uniform p.
Reorientations have Poissonian statistics in time. The amplitude of the LSC and the magnitude of the
azimuthal rotation rate have a negative correlation.
DOI: 10.1103/PhysRevLett.95.084503 PACS numbers: 47.27.Te, 05.65.+b
A major component of turbulent Rayleigh-BeŽnard con-
vection  in a fluid heated from below is the emission
of hot (cold) volumes of fluid known as ``plumes'' from
bottom (top) thermal boundary layers. These plumes are
carried by, and by virtue of their buoyancy, in turn drive a
large-scale circulation (LSC)  known as the ``mean
wind.'' For cylindrical samples of aspect ratio ÿ D=L '
1 (D is the sample diameter and L the height) the LSC is a
circulation in a near-vertical plane with upflow and down-