The flow interaction between a stationary cylinder and a downstream flexible cylinder

This paper deals with an experimental investigation of the dynamic response of a long flexible circular cylinder in the wake of a stationary geometric ally similar cylinder. The system has a low damping ratio. The tandem and s taggered arrangements have been considered. The separations investigated ar e typical of transmission line bundles and range from 7 to 25 diameters and Reynolds number ranges from 5 000 to 27 000. For the tandem cylinders, the results indicate that (a) the dynamic response of the downstream cylinder is no longer hysteretic, (b) the synchronization onset is at higher reduced velocities and (c) the synchronization region is wider than that of an iso lated cylinder; this region is twice as large for a separation of 10 diamet ers and decreases with increasing spacing. Despite the absence of the hyste resis loop and its associated discontinuities, two vortex patterns are pres ent around the resonance velocity. A small decrease of the maximum amplitud e of oscillation with increasing spacing has also been observed, as well as a reduction of the velocity for which this maximum occurs. For separations of 7 and 85 diameters, the leeward cylinder exhibits a combination of vort ex-induced and wake-galloping oscillations. For the staggered arrangement, the increase of the stagger angle beta reduces the synchronization onset ve locity and the synchronization region and beyond beta = 20 degrees the down stream cylinder behaves as an isolated one. (C) 1999 Academic Press.