Energy harvesting from vortex-induced vibrations of a pendular circular cylinder in cross-flow*

A pendulum based on a rigid circular cylinder has been designed to study one degree-of-freedom vortex-induced vibration (VIV)  in cross-flow. The system consists of cylinder with mass m, length L and diameter D, that hangs from an air bearing rig to minimise damping, whilst restoring forces are provided by a pair of springs with stiffness constant k. A torsion load cell has been installed at the rotation shaft of the cylinder, between the model and an electromagnetic powder brake. The brake allows to precisely adjust the torque on the shaft. The angular motions of the cylinder are measured using a non-intrusive laser sensor.The cylinder is exposed to a uniform flow with velocity U, generated by the free surface water channel at the Laboratory for Fluid-Structure Interaction (LIFE) at Universitat Rovira i Virgili.

The dynamic response of the system is fully characterized, including measurements of amplitude and frequency of oscillation, mechanical power output, flow visualization, as well as estimations of the fluid excitation. The experiments covered a large parametric space, consisting of variations of the free stream velocity, leading to a wide range of reduced velocities and Reynolds numbers. The rich fluid-structure interaction phenomena observed in the experiments will be discussed and analyzed in detail.