Flow-induced vibrations of a rotating cylinder in an arbitrary direction

An elastically mounted circular cylinder, immersed in a cross-current and forced to rotate about its axis, represents a paradigm to explore the impact of symmetry breaking on flow-structure interactions. Previous works have shown that when the rotating body is free to translate in the direction normal to the current, its responses are comparable to the vortex-induced vibrations (VIV) developing in the absence of rotation, regardless the value to the rotation rate: synchronization of wake unsteadiness and body motion, bell-shaped evolution of the vibration amplitude as a function of the reduced velocity (inverse of the oscillator natural frequency). On the other hand, when the direction of motion is aligned with the current, the system undergoes, at high rotation rate, a switch from VIV-like oscillations to galloping responses, with amplitudes continuously increasing with the reduced velocity. The transition between the contrasted behaviors observed in these two configurations remained to be clarified; this is the object of the present numerical study, where the orientation of the vibration plane is introduced as a new parameter of the problem. Particular attention is paid to the emergence of the galloping-like response regime and its possible modeling by a quasi-steady approach.