Stability of the vortex motion in oscillating flow.
stabilityofvorte00mcco.pdf (5.137Mb)Abstract
Previous experimental investigations have shown that the characteristics of flow
about a circular cylinder immersed in a time-dependent flow exhibit cycle-to-cycle
variations. These variations have been attributed to the variations in the spanwise
coherence, aspect ratio, nonuniformity of the flow, and random disturbances in the
ambient flow. A theoretical investigation was undertaken to examine the stability of
the flow characteristics in terms of the initial state of the vortices. An idealized model
has been devised and the position of the vortex was varied systematically. The results
have shown that finite-precision information about the characteristics of the flow does
not lead to finite-precision information at a later stage. In fact the advection of the
vortices can give rise to chaotic behavior in the calculated lift and drag forces and in
the velocity field. It is concluded that the cycle-to-cycle variations are not entirely due
to lack of spanwise coherence and that they are mostly a consequence of the chaotic
motion which can result from the advection of the vortices in a time-dependent flow.
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