Enhancing energy harvesting from flow-induced vibrations of a circular cylinder using a downstream rectangular plate: An experimental study

Abstract

Vortex-induced vibration (VIV)-based energy harvester with a circular cylinder as a bluff body is a classic choice for harvesting wind energy, while it is only effective in a limited wind speed range known as the lock-in or synchronization region. To enhance the effectiveness of circular cylinder-based energy harvesting systems, this effort proposes the concept of placing an interference rectangular plate in the wake of the circular cylinder with determining the most effective design of the rectangular plate location and dimension. A series of wind tunnel experiments are conducted to prove the usefulness of the downstream rectangular plate and how it positively or negatively affect the harvester's efficacy. The width of the plate is 1D, three height scenarios of the plate are considered, namely, 1D, 2D, or 3D, and the space between the cylinder and the plate is varied between 0.1D to 2.0D, where D is the cylindrical diameter. Experimental results show that for a specific plate height, galloping-type response (i.e., full interference between galloping and VIV), partial interference between galloping and VIV, and lock-in-type response are observed successively with increasing the space between the cylinder and the plate. The galloping-type response, which often occurs when a rectangular plate is placed close to the circular cylinder, can dramatically increase the effective wind speed range for energy harvesting and the generated voltages at higher wind speeds. The most effective design scheme among the tested cases is a 2D-high plate placed around 0.2D ∼ 0.4D downstream of the circular cylinder. The downstream rectangular plate can work as a competitive candidate for enhancing the performance of a circular-based energy harvester due to its effectiveness and reduced cost than other aerodynamic modification measures that are spanned over the whole length of the circular cylinder.