A series of experiments were performed using multiple configurations of hydrofoils to assess the energy harvesting capabilities present within the wake of streamlined bodies. The experiments were performed in a low-speed water tunnel, with energy harvesting assessed using a piezoelectric eel and imaging equipment. Half-sinusoidal undulations were introduced in different combinations on the leading and trailing edges of the hydrofoil. All hydrofoils utilized a NACA 0012 cross-sectional profile. A piezoelectric eel was placed at a variable distance downstream of the hydrofoil’s trailing edge, and the hydrofoil’s angle of attack (α) was varied in order to assess the variation in power generation. The maximum power output was achieved at x/c = 1–1.5 downstream of the trailing edge in all configurations. It was observed that harvested energy is dependent on the oscillation of the eel, α, the streamwise distance between the trailing edge of the hydrofoils and the eel, as well as the geometry of the hydrofoils. Particle image velocimetry was also performed on selected cases for which the recorded energy harvest was high. The results showed that the NACA 0012 base profile has a higher extractable energy capacity in its wake than do the serrated hydrofoils, which confirms the results found in the literature.

Piezoelectric energy harvesters are considered a replacement for batteries because they are self-sustainable with low or no maintenance, and suitable for off-grid devices. In this study, two cylinders were placed in a flowing stream of water. The upstream cylinder of 25 mm diameter is fixed at the center of the stream while another cylinder of the same diameter, which is free to oscillate in the crosswise direction of the flow and is placed in the wake of that fixed cylinder. A piezoelectric flag is then placed in the wake of the vibrating cylinder and its distance from the vibrating cylinder was changed to observe the effect of wake length on the energy harvester. The energy harvesting potential of the system is explored for flow velocities ranging from 0.28 m/s to 0.36 m/s. The distance between the cylinders Gx, which is explored for the range of 2.5D–7D, and the distance between the piezoelectric membrane and the vibrating cylinder are expressed as Sx for the same range. The maximum power of 19.17 μW was produced at Sx = 2D and Gx = 3.5D. The maximum power for the baseline case, when two tandemly arranged stationary circular cylinders were used and a piezoelectric membrane was placed in their wake, is 10.24 μW; hence, an increase of 87.2% is observed under the same ambient conditions.