Enhancing the Performance of an Oscillating Wing Energy Harvester Using a Leading-Edge Flap

Abstract

In this study, we investigated the power generation capability of an oscillating wing energy harvester featuring an actively controlled flap positioned at the wing’s leading edge. The findings revealed that attaching a leading-edge flap reduces fluid flow separation below the wing’s lower surface at the leading edge, resulting in smoother flow and increased velocity near the hinge region. The leading-edge flap increases the pressure difference across the wing’s surface, thereby enhancing the overall performance. In addition, the introduction of the leading-edge flap effectively elongates the wing’s effective projected length in the heaving direction, leading to increased thrust. We examined flap lengths ranging from 10% to 50% of the chord length, with the maximum pitch angles of the wing and flap varying from 75° to 105° and 30° to 55°, respectively. The optimal power generation was achieved using a flap length of 40% of the chord length, combined with maximum wing and flap pitch angles of 95° and 45°, respectively. These conditions yielded a 29.9% overall power output increase and a 20.2% efficiency improvement compared to the case without the leading-edge flap.

Numerically Investigating the Energy-Harvesting Performance of an Oscillating Flat Plate with Leading and Trailing Flaps

“…A study investigating the impact of extending the trailing edge flap on a flapping wing revealed an increase of 26.9% in power and a 21% improvement in performance at a 60% flap length [54]. Similar success was achieved with leading-edge flaps, with a study finding a configuration that boosted power by 29.9% and efficiency by 23% [55]. Extensive studies have been conducted on the use of flaps in applications involving single blades and vertical-axis wind turbines [56][57][58].…”

“…The output power C pt = 1.183 for the wing with a leading flap is higher than the output power C pt = 1.177 for the wing with a trailing flap, showing the importance of the leading flap. These specific percentages with their pitch angles for a wing with a flap were selected in this study because they yield the most efficient energy extraction, as noted by [54,55], and for a wing without any flaps, as noted by [62].…”

“…The length percentages and the pitch angles for the wing with the leading flap are shown in Table 2. This wing with a leading flap, marked by the black point in Figure 5a,b, is the optimum case study as mentioned in [55]. The oscillating flat plate with two flaps (L30, W55, and T15) shows a notable performance, achieving an output power C pt of 1.225 and an efficiency η of 45.30%, which surpass the corresponding values of 1.183 in C pt and 43.01% in η observed for the wing with a leading flap.…”