Suppression of electroconvection by Couette shear in freely
suspended smectic C* films
Suppression of electroconvection by Couette shear in freely
suspended smectic C* films
Molecular Crystals and Liquid Crystals, 367, 113 (2001).
Christian Langer (1),
Zahir A. Daya (2),
Stephen W.
Morris (2) and
Ralf
Stannarius (1).
(1) Universitat Leipzig, Linnestrasse 5,
04103 Leipzig, Germany
(2) Department of Physics,
University of Toronto, 60 St. George St., Toronto, Ontario, Canada M5S 1A7.
We present the first experiments on electrohydrodynamic convection with a
superposed Couette shear in freely suspended annular smectic C*
films. Similar experiments on smectic A films have been carried out
previously. In those experiments, surface-charge driven electroconvection in
combination with shear leads to a pattern
of travelling convective vortices. Travelling vortex patterns are also
observed in smectic C* films. In contrast to smectic A films,
however, the flow field in C* films is coupled to c-director
orientation effects that allow a direct visualization of the periodic flow
pattern. The critical voltage for the onset of convection was determined by
electric current measurements and compared with corresponding results for
smectic A films. Measurements at various shear rates show that the onset is
suppressed by the shear.
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