Author:
KOLÁŘ V.,LYN D. A.,RODI W.
Abstract
The ensemble-averaged characteristics of the turbulent near-wake
flow around two side-by-side identical square cylinders at a Reynolds number
≈23100 have been
studied using a two-component laser-Doppler velocimeter system. The work
focuses
on a single case with a gap/diameter ratio of 2, for which the
resulting individual
vortex streets are coupled so as to yield a flow predominantly symmetric
about
the line midway between the two cylinders. Data sorting or conditioning
according
to phase was performed with the aid of pressure signals taken from taps
on a
sidewall of each cylinder. The two-cylinder results are compared in detail
to results
from a previous study of the one-cylinder case. Vortex structures shed
on the side
towards the flow centreline, termed inner structures, are distinguished
from those
shed on the free-stream side, termed outer structures, and the
differences between the
features associated with the two different structures are examined. The
circulation
associated with outer structures evolves downstream in a manner similar
to that
observed in the one-cylinder case, but the circulation of the inner structures
is
found to decrease dramatically downstream. This not only gives support
to previous
theoretical predictions but also reconciles these with
previously apparently conflicting
experimental observations. Information regarding vortex structure motion
and the
relevant length and time scales is obtained. Differences between momentum
and
vorticity transport, particularly across the flow centreline are
pointed out, and effective
turbulent vorticity fluxes are defined. Similarities in local flow
topologies in one- and
two-cylinder cases are discussed, and the role of local velocity-gradient
invariants and
their relationship to critical points and turbulence statistics are examined.
Publisher
Cambridge University Press (CUP)
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics
Cited by
95 articles.
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