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VOLUME 83, NUMBER 25 P H Y S I C A L R E V I E W L E T T E R S 20 DECEMBER 1999 Wave Number Selection and Large-Scale-Flow Effects due to a Radial Ramp of the Spacing
 

Summary: VOLUME 83, NUMBER 25 P H Y S I C A L R E V I E W L E T T E R S 20 DECEMBER 1999
Wave Number Selection and Large-Scale-Flow Effects due to a Radial Ramp of the Spacing
in Rayleigh-Bénard Convection
Kapil M. S. Bajaj, Nathalie Mukolobwiez, Nathan Currier, and Guenter Ahlers
Department of Physics and Quantum Institute, University of California, Santa Barbara, California 93106
(Received 23 July 1999)
We present experimental results for wave numbers qs selected in a thin horizontal fluid layer heated
from below. The cylindrical sample had an interior section of uniform spacing d d0 for radii
r , r0 (G0 r0 d0 43) and a ramp d r for r . r0. For Rayleigh numbers R0 . Rc 1708 in
the interior, straight or slightly curved rolls with an average qs ~qc 1 ae0 e0 R0 Rc 2 1 and
~qc , qc 3.117 were selected, and qs varied on two length scales approximately equal to G0 and to
four roll wavelengths. For e & 0.03 and e * 0.18 the pattern repeatedly formed defects.
PACS numbers: 47.54.+r, 47.20.Bp, 47.20.Lz, 47.27.Te
Many spatially extended nonlinear nonequilibrium sys-
tems undergo a transition from a uniform state to a state
with spatial variation (a "pattern") when a control parame-
ter R exceeds a critical value Rc [1]. Convection in a thin,
wide horizontal fluid layer confined between two parallel
rigid plates and heated from below [Rayleigh-Bénard con-
vection (RBC)] has long been a paradigm of pattern for-

  

Source: Ahlers, Guenter - Department of Physics, University of California at Santa Barbara

 

Collections: Physics