On vortex-induced vibrations of cylinders describing X-Y trajectories

This paper examines the 2S and 2P wake flow modes and their respective domain under configurations differing from that of free oscillations in the cross-flow direction only. A proposed dimensionless variable, a, defining a velocity plane of vibration is shown to link results obtained under X-Y motion to observations made with mechanically constrained oscillations. This variable, a, attempts to evaluate how far the conditions of motion are from that of a pure Y motion and associates the corresponding modes of vortex shedding: this variable corresponds to aretan[(dX/dt)/(dY/dt)]. The 2P mode is observed to cease to occur as the transverse vibration plane is inclined at angles alpha > 30 degrees with respect to the cross-flow direction. Although the onset of vortex-induced vibrations is observed to remain identical in the range 0 <= a <= 45 degrees, the synchronization range is reduced with increasing a. The critical curve, detected from the experimental occurrence of bifurcations, is gradually shifted as a is increased. (c) 2006 Elsevier Ltd. All rights reserved.