 
Summary: Traveling concentricroll patterns in RayleighBeŽnard convection with modulated rotation
Kim L. Thompson, Kapil M. S. Bajaj, and Guenter Ahlers
Department of Physics and iQuest, University of California, Santa Barbara, California 93106
Received 10 October 2001; published 5 April 2002
We present experimental results for pattern formation in RayleighBeŽnard convection with modulated rota
tion about a vertical axis. The dimensionless rotation rate was varied as m 1 cos( t) time is
scaled by the vertical viscous diffusion time of the cell . We used a cylindrical cell of aspect ratio radius/
height 11.8 and varied , , , and R/Rc( ) 1 (R is the Rayleigh number . The fluid was water
with a Prandtl number of 4.5. Sufficiently far above onset even a small 0.02 stabilized a concentricroll
target pattern. Multiarmed spirals were observed close to onset. The rolls of the target patterns traveled
radially inward independent of the sense of rotation. The radial speed v was nearly independent of for fixed
, , and . However, v increased with any one of , , and when all the other parameters were held fixed.
DOI: 10.1103/PhysRevE.65.046218 PACS number s : 47.54. r, 47.32. y, 47.27.Te
Convection in a thin horizontal layer of fluid heated from
below, known as RayleighBeŽnard convection RBC , pre
sents a rich variety of phenomena when the control param
eter is modulated. The usual control parameter is the Ray
leigh number R gd3
T/ , where is the isobaric
thermal expansion coefficient, g the vertical acceleration, T
