Sensitivity of transition phenomena to small perturbations in flow round a circular cylinder

Abstract

In the critical Reynolds-number range ( Re = 3−4 × 10 5 ) the structure of the flow around a circular cylinder undergoes drastic changes that are coupled with a break in symmetry manifested by the occurrence of a steady lift force having unpredictable sign. Between the stable states the time functions of lift exhibit chaotic behaviour. Sensitivity to small perturbations is demonstrated by experiments showing that in principle it is possible to trip all transition jumps in the critical range by a perturbation localized in space and time. The structural changes of the flow, in particular the symmetry breaks, are visualized by oil-flow photographs. Furthermore the transition jumps were recorded in the time domain, thus the characteristic time for the jumps was obtained.