Wake dynamics in the lower branch and desynchronization regions of 1DoF Viv

Vortex induced vibrations of a circular cylinder has been investigated experimentally using a cyber-physical apparatus with m^∗ = 8 and ζ = 0.005. The Reynolds number is held fixed at Re = 4000, with the reduced velocity being modified via a change in the structural natural frequency in a cyber-physical controller. A detailed analysis of lower branch and desynchronization regions of VIV is presented through Proper Orthogonal Decomposition and Phase Averaging. An alternative methodology for extracting coherent motions from the wake flow is proposed by performing a POD analysis on the residual error field of the phase-averaged flow. The results demonstrate that coherent motions of the cylinder wake can either provide damping or excitation to the cylinder motion, and this is captured within the third most energetic POD mode.