Piezoelectric energy harvesting from cantilevered-rectangular bluff bodies using fluid-structure interaction

Rigid rectangular bluff bodies of varying B/D ratios attached to two piezoelectric cantilevers are subjected to vortex-induced vibrations (VIV) and flutter in a suction-type wind tunnel to study the influence of different flow-induced vibrations. The cantilevered-rectangular bluff bodies were arranged in a parallel configuration to aid in vibration frequency control. Images of the vibrating cylinders were captured at high speeds and compared with the voltage levels generated as a function of incident wind speed. The ratio of natural frequency to vibration frequency proved to be an indicator of operating efficiency. The energy harvesting efficiency of the bluff bodies was also calculated and was shown to be dependent on the frequency ratio. The maximum power harvested was found to be 1.8μW. An operating limit for each bluff body of a given B/D ratio was established in terms of non-dimensional parameters such as Reynolds number (Re)-(1500-5500), Strouhal number (St)-(0.06-0.16), Dimensionless frequency (0.1-0.7), Scruton number (Sc) and reduced velocity (4-14).  Beyond the operating limit, no positive effect on the resultant voltage was observed. These results will further aid the design and development of vibration-based ambient energy harvesters.