Vortex-induced vibrations in the presence of moderate freestream turbulence

The influence of incoming freestream turbulence on an elastically mounted circular cylinder undergoing vortex-induced vibrations is investigated through simultaneous displacement and flow field measurements at a constant Reynolds number of approximately 4400. The results show that the effects of freestream turbulence are more prominent within the lower branch and desynchronization, where earlier desynchronization is observed with elevated freestream turbulence. Conversely, freestream turbulence minimally affects the structure and wake dynamics within the initial and upper branches. A comparison between a stationary cylinder wake and the wake of a cylinder free to vibrate at very low amplitudes reveals that even minor cylinder vibrations ( approximate to 1% of cylinder diameter) modify the separated shear layer and near wake dynamics, the result of which is a decreased sensitivity of the near wake to freestream turbulence. Proper orthogonal decomposition is used to identify changes in the vortex shedding characteristics that result in earlier desynchronization.