NUST Institutions Library Catalogue

The increasing global demand for sustainable and efficient energy sources due to
environmental concerns is pressing. Energy harvesting from fluid flows provides a promising
option for renewable energy generation, and the development of self-sustaining devices is crucial
for practical implementation. In this regard, the need to study the impact of varying the size of
bound region on energy harvesting is necessary, which is significant for the optimal design of
portable devices due to the establishment of boundary layer. Therefore, this experimental study
aims to investigate the effect of changing the distance between wall boundaries on the performance
of a piezoelectric-based energy harvester in generating electrical energy from fluid flow. A series
of experiments were conducted to analyze the dynamical behavior of a piezoelectric flag due to
gap variation and the impact of boundary layer thickness (δ) on its behavior. The setup involved
placing inverted C-shaped (120-degree cut) and circular cylinders in a uniform fluid flow, utilizing
the undulating motion of the piezo flag in the downstream vortices to harvest electrical energy.
The distinct flapping modes were observed in the experimental results which can create varying
degrees of coupling in the wake flow. The dynamic behavior of the piezoelectric flag was observed
to be influenced by both the gap between cylinder and flag (Dx) and Cylinder to wall (Dy), leading
to output power fluctuation. For each 𝑥
∗ value, the power output levels were analyzed by
experimentally varying Dx values from 1.0 to 5.0 for different values of Dy in terms of δ to find
the optimal configuration. The cylindrical arrangement of both bluff bodies, characterized by Dy
= 34.05δ and 𝑥
∗ = 310 mm, exhibits a persistent pattern of peak power output within the range of
2.0 ≤ Dx ≤ 3.0 due to continuous flapping and significant amplitudes. The inverted C-shaped
cylinder (120o
cut) shows a maximum gain of 83% in power output compared to the circular
cylinder. Furthermore, it is demonstrated that certain spanwise gaps lead to low energy production
due to boundary viscous effects and poor coupling of wake flow. This study provides valuable
insights into the development of more efficient and optimal sustainable devices for remote
practical applications and renewable energy sources, reducing dependence on conventional
sources.