Analysis of Wake Region Behind Bluff Body for Piezoelectric Energy Harvester
Keywords:Piezoelectric film, bluff body, wake region, vortex shedding frequency, vorticity, pressure difference
Inspired by enhancement of vortex induced vibration energy harvesting as a green and renewable energy source, several geometry shapes such as cylinder, square, triangle, D shape, and U shape bluff body were studied in terms of vortex shedding frequency, vorticity and pressure difference in order to determine the best bluff body for piezoelectric film. A 2-dimensional computational fluid dynamic (CFD) simulation analysis is carried out with the length and height of bluff body fixed as 0.1 m and air flow used for simulations are 0.0438 m/s, 0.292 m/s, and 0.73 m/s which corresponds to Reynolds number (Re) of 300, 2000, and 5000. Overall, cylinder, triangle, and D shape bluff body gives a higher vortex shedding frequency and Strouhal Number (St) compare to square and U shape. Triangle bluff body was able to maintain the highest vorticity for all three difference air speeds. It is found that maximum vorticity point will move backwards when higher air velocity is simulated. Nevertheless, triangle bluff body gave the highest-pressure difference reading among all tested shapes. In conclusion, triangle shape bluff body is the most suitable shape for inducing vortex shedding to piezoelectric film and it is suggested the length of the piezoelectric beam is between 0.05m and 0.15m.