Energy harvesting based on flow-induced vibration of a wavy cylinder coupled with tuned mass damper

Abstract

We investigate the flow-energy harvesting performance of a system consisting of a wavy cylinder and a tuned mass damper (TMD), through experiments, theoretical modeling and CFD simulations. The wavy cylinder is elastically supported, being able to oscillate transversally in cross flows and further enforcing a piezoelectric sheet to generate electricity. Results indicate that the output power strongly depends on wavelength λz, amplitude a, and the tip mass of TMD. The wavy cylinder outperforms the smooth cylinder when λz≥ 3.6Dm and peaks at λz = 6.0Dm and a = 0.25Dm with an improvement of 70%. This superiority also exists in a wider range of reduced velocities, leading to a power increase of 121%. The behavior of the oscillation echoes the observations made on the energy. The flow field results reveal that at λz = 6.0Dm and a = 0.25Dm, hairpin vortexes with legs attaching on the two sides of the node are observed, producing a wide wake near the node while a narrow wake near the saddle. However, an opposite scenario is observed for the case with the worst performance, i.e., λz = 1.8Dm and a = 0.25Dm. The former wake distribution seems to create a larger pressure difference over the wavy cylinder, induce a larger oscillation and hence improve the power output.