A comparative study of dual cylinders and triangle bluff bodies for piezoelectric energy harvesting

Abstract

The flow patterns behind tandem bluff bodies can be used to generate electricity in piezoelectric energy harvesters. The vortices and wakes that form behind the bluff bodies create a pressure differential, which can be used to deform a piezoelectric film. In this study, we investigated the performance of dual triangle and dual cylinder bluff bodies in tandem at varying Reynolds numbers, Re, and spacing ratios, D. We compared the flow patterns behind the two types of bluff bodies. Sixteen hot wire anemometers were placed at different locations to measure the velocity developed behind the dual bluff bodies in tandem. The results showed that the velocities behind the cylinder bluff bodies were initially higher than those behind the triangle bluff bodies at lower Re. This is because the cylinder bluff bodies create a more turbulent flow, which results in higher velocities at lower Re. The best distance between the two bluff bodies was 3D and 5D, where the output velocities were maximized at more than 12ms−1. However, for dual triangle, the velocities eventually became higher than those behind the cylinder bluff bodies at higher Re and lower separation ratios (1D and 2D). 3D was the best distance for triangle to produce a higher velocity pattern, and this was best observed when Re = 10k, which is the lowest inlet velocity set. The results of the experiments are expected to show that the dual triangle bluff bodies produce higher velocities than the dual triangle bluff bodies, which will lead to a higher amount of energy being harvested. The results show that the amount of energy harvested were increase with increasing Re and decreasing D. The information enhancement can be done with turbulence analysis which could lead to the development of more efficient and versatile piezoelectric energy harvester.