Modes of synchronisation in the wake of a streamwise oscillatory cylinder
A numerical analysis of flow around a circular cylinder oscillating in-line with a steady flow is carried out over a range of driving frequencies $(f_{d})$ at relatively low amplitudes $(A)$ and a constant Reynolds number of 175 (based on the free-stream velocity). The vortex shedding is investigate...
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Published in | Journal of fluid mechanics Vol. 832; pp. 146 - 169 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
Cambridge, UK
Cambridge University Press
10.12.2017
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Subjects | |
Online Access | Get full text |
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Summary: | A numerical analysis of flow around a circular cylinder oscillating in-line with a steady flow is carried out over a range of driving frequencies
$(f_{d})$
at relatively low amplitudes
$(A)$
and a constant Reynolds number of 175 (based on the free-stream velocity). The vortex shedding is investigated, especially when the shedding frequency
$(f_{s})$
synchronises with the driving frequency. A series of modes of synchronisation are presented, which are referred to as the
$p/q$
modes, where
$p$
and
$q$
are natural numbers. When a
$p/q$
mode occurs,
$f_{s}$
is detuned to
$(p/q)f_{d}$
, representing the shedding of
$p$
pairs of vortices over
$q$
cycles of cylinder oscillation. The
$p/q$
modes are further characterised by the periodicity of the transverse force over every
$q$
cycles of oscillation and a spatial–temporal symmetry possessed by the global wake. The synchronisation modes
$(p/q)$
with relatively small natural numbers are less sensitive to the change of external control parameters than those with large natural numbers, while the latter is featured with a narrow space of occurrence. Although the mode of synchronisation can be almost any rational ratio (as shown for
$p$
and
$q$
smaller than 10), the probability of occurrence of synchronisation modes with
$q$
being an even number is much higher than
$q$
being an odd number, which is believed to be influenced by the natural even distribution of vortices in the wake of a stationary cylinder. |
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ISSN: | 0022-1120 1469-7645 |
DOI: | 10.1017/jfm.2017.655 |