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, α, 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, α, 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 arctan[(dX/dt)/(dY/dt)]arctan[(dX/dt)/(dY/dt)]. The 2P mode is observed to cease to occur as the transverse vibration plane is inclined at angles α>30°α>30° with respect to the cross-flow direction. Although the onset of vortex-induced vibrations is observed to remain identical in the range 0⩽α⩽45°0⩽α⩽45°, the synchronization range is reduced with increasing α. The critical curve, detected from the experimental occurrence of bifurcations, is gradually shifted as α is increased.