Abstract:
We describe a numerical procedure to construct a modified
velocity field that does not have any mean flow. Using this
procedure, we present two results. First, we show that, in
the absence of the mean flow, spiral defect chaos collapses
to a stationary pattern comprising textures of stripes with
angular bends. The quenched patterns are characterized by
mean wave numbers that approach those uniquely selected by
focus-type singularities, which, in the absence of the mean
flow, lie at the zigzag instability boundary. The quenched
patterns also have larger correlation lengths and are
comprised of rolls with less curvature. Secondly, we
describe how the mean flow can contribute to the commonly
observed phenomenon of rolls terminating perpendicularly
into lateral walls. We show that, in the absence of the mean
flow, rolls begin to terminate into lateral walls at an
oblique angle. This obliqueness increases with the Rayleigh
number
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