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This study investigates the power generation capability of an oscillating wing energy harvester equipped with two actively controlled flaps positioned at the leading and trailing flaps of the wing. Various parameters, including flap lengths and pitch angles for the leading flap and trailing flap, are explored through numerical simulations. The length of the main wing body ranges from 40% to 65% of the chord length, c, while the leading and trailing flaps vary accordingly, summing up to the total length of the flat plate c = 100%. The pitch angles of the two flaps are adjusted within predefined limits. The pitch angle for the leading flap varies between 25° and 55°, while the trailing flap’s angle ranges from 10° to 40° across 298 different simulation scenarios. The results indicate that employing both leading and trailing flaps enhances the power output compared to a wing with a single flap configuration. The trailing flap deflects the incoming fluid more vertically, while the leading flap increases pressure difference across the surface of the main wing body, synergistically improving overall performance. The power output occurs at a specific length percentage: a leading flap of 30%, a main wing body of 50%, and a trailing flap of 20%, with pitch angles of 50°, 85°, and 30°, respectively, increasing the output power increments by 4.39% compared to a wing with a leading flap, 4.92% compared to a wing with a trailing flap, and 28.24% compared to a single flat plate. The highest efficiency for the specified length percentages is 40.37%.

This study proposes a hybrid pitching motion for oscillating flat plates aimed at augmenting the energy extraction efficiency of an energy harvester. The proposed hybrid pitching motion, within the first half cycle, integrates a non-sinusoidal movement starting at t/T = 0 and progressing to t/T = 0.25, with a sinusoidal movement initiating after t/T > 0.25 and continuing to t/T = 0.5. The second half of the cycle is symmetric to the first half but in the opposite direction. The calculated results show that the proposed hybrid pitching motion outperforms both the sinusoidal and the non-sinusoidal motions. The hybrid pitching motion merges the merits of both the sinusoidal and non-sinusoidal motions to optimize pitch angle variation. This integration is pivotal for enhancing the overall power output performance of an oscillating energy harvester characterized by momentum change that enhances the orientation of the heaving movement, smoother motion transitions, and consistent energy harvesting. The power generation is obtained at wing pitch angles of 55°, 65°, 70°, 75°, and 80° during a hybrid pitching motion. The proposed hybrid pitching motion, set at a pitch angle of 70°, achieves a maximum power output that exceeds the oscillating flat plate using a sinusoidal pitching motion by 16.0% at the same angle.

This study applied a hybrid pitching motion for an oscillating wing with a leading flap aimed at enhancing energy extraction efficiency. In the first half of the cycle, the hybrid pitching motion begins with a non-sinusoidal pitching motion for 0.0 ≤ t/T ≤ 0.25, transitioning to a sinusoidal pitching motion for 0.25 < t/T ≤ 0.50. The latter half of the motion mirrors the first one but moves toward the reverse direction. Hybrid motions combine the benefits of non-sinusoidal and sinusoidal pitching motions, enhancing the optimization of pitch angle variation. The findings show that hybrid motions for the wing fitted with an attached leading flap outperform both the single plate and the wing with an attached flap using sinusoidal pitching motion. The simulation was conducted with flap lengths ranging from 30% to 45% of the chord length and examined maximum pitching angles of the wing and the attached leading flap between 80° to 95° and 25° to 60°, respectively. By setting the pitch angles of the wing and leading flap to 85° and 45°, respectively, with the wing comprising 65% of the total length and the leading flap 35%, the proposed hybrid pitching motion with the leading flap generates a maximum power output of 1.276 that surpasses that of a sinusoidal pitching motion of 0.963 on an oscillating flat plate by 32.50%. This combination of hybrid pitching motion and a wing flap configuration is effective in improving the performance.

This study investigates the impact of different duct designs on the energy-harvesting performance of oscillating-wing systems in both partially and fully confined environments. Numerical simulations were conducted to examine the effects of straight, convergent–straight, and convergent–divergent duct configurations on the aerodynamic forces and overall energy extraction efficiency. Under partial confinement, the convergent–divergent duct demonstrated a significant improvement of 67.5% in power output over the ductless baseline configuration. This enhancement is attributed to the increased incoming flow velocity and amplified pressure difference around the wing, which improve the effectiveness of energy generation. However, the straight and convergent–straight ducts reduced the harvester’s performance due to the diminished flow velocity within each duct. Under full confinement, all duct configurations substantially enhanced energy-harvesting performance, with the convergent–straight duct providing the highest efficiency gain (84.9%). This improvement is primarily due to the increased velocity and pressure differential across the wing surfaces, which maximise the heaving force and overall energy generation performance. These findings highlight the critical role of duct geometry in optimising energy-harvesting performance, both in partially confined and fully confined flow environments.

Flapping wings present a promising approach to harnessing energy from fluid flow by leveraging a synchronized pitching and heaving motion of the airfoil. The impact of modifying the leading and trailing edge shapes of a flapping wing on energy harvesting performance is investigated using sinusoidal pitching motion. The pitch angle varies between 80° and 90°. The wing thickness (T1) varies from 8% to 48% of the chord length, with a flat plate chord length of c = 1.0. A promising airfoil profile is achieved by increasing only the leading-edge thickness to 32% of the chord, significantly enhancing energy capture by improving the generation of pushing forces and power. The results show that a wing configuration with a semicircular leading edge and a rectangular trailing edge outperforms the baseline case (a rectangular flat plate) and all other configurations under the same conditions. This configuration shows a notable improvement in power output and efficiency at a pitch angle of 85° and a leading-edge thickness of 32% of the chord. The maximum power output (Cpt) represents a 16.73% increase over the baseline, while the maximum efficiency (η) reflects a 12.77% improvement. These findings highlight the superior energy extraction performance of the new configuration, emphasizing the dominant role of the leading edge in enhancing energy harvesters compared to the trailing edge.

This research utilized a hybrid trajectory on a wing incorporating a dual flap with the goal of enhancing performance. The hybrid profiles initiate with a non-sinusoidal pattern during the interval 0.0 ≤ t/T ≤ 0.25, evolving toward a sinusoidal pattern within the range 0.25 < t/T ≤ 0.5. Similarly, the hybrid motion follows a non-sinusoidal pattern in the range 0.5 < t/T ≤ 0.75, before shifting back to a sinusoidal pattern within the range 0.75 < t/T ≤ 1.0. The effectiveness of using a hybrid trajectory on a wing with leading and trailing flaps in enhancing the energy harvesting performance is examined through numerical simulations. The results demonstrate that hybrid trajectories applied to a two-flap wing configuration outperform a single flat plate and a wing with leading and trailing flaps both operating under a sinusoidal trajectory. The wing length spans from 45% to 55%, with the leading flap length ranging from 25% to 35%. The trailing flap lengths adjust accordingly to ensure the combined total matches the flat plate’s full length, which is 100%. The wing pitch angle was fixed at 85° while the leading flap’s pitch angle varied between 40° and 55° and the pitch angle of the trailing flap ranged from 0° to 20°. The findings reveal that utilizing hybrid motion on a wing fitted with leading and trailing flaps notably improves power output in comparison to configurations with either one plate or three plates. The power output is achieved at particular dimensions: a leading flap length of 30%, a wing length of 55%, and a trailing flap length of 15%. The corresponding pitch angles are 50° for the leading flap, 85° for the wing, and 10° for the trailing flap. The aforementioned configuration results in a 34.06% increase in output power in comparison to one plate. The maximum efficiency for this setup reaches 44.21%. This underscores the superior performance of hybrid trajectories over sinusoidal trajectories in enhancing energy extraction performance.

This study investigates the unsteady incompressible flow around a square cylinder with different chamfer ratios (CRs) using a commercial finite volume code, ANSYS Fluent. CR ranges from 0.0 (sharp square cylinder) to 0.5 (diamond cylinder) with variable increments. Detailed analysis of flow characteristics is conducted at Reynolds number (Re) = 2100. Additionally, simulation is extended to cover Re, i.e., Re = 100, 500, and 10000. The simulation results show that cylinder with CR = 0.1 outperforms all other cases by enabling a drag reduction of about 60 % at Re = 104. Drag has an inverse relationship with the wake closure length. Time-averaged coefficient of pressure, streamlines, and vorticity contours are also discussed to better understand near-wake features and the physics of drag reduction.

The formation of the electrolyte–electrode interface is essential for the performance of Li-ion batteries. This study aims to explore the wetting characteristics of an electrolyte within a porous electrode positioned between a current collector and a separator. By utilizing the Shan-Chen-based lattice Boltzmann method, an in-house code has been developed and thoroughly validated. This code integrates actual contact angles at the interfaces between the electrolyte and battery components. Furthermore, code acceleration through GPU-based parallel programming facilitates adequate meshing, underscoring the novelty and originality of our approach. The results of this study provide insights into the overall saturation curves and imbibition rates and clarify the primary mechanisms of electrolyte wetting within the porous matrix via local wetting rates. The electrode-current collector interface emerged as a critical factor influencing the imbibition rate and gas entrapment tendencies. Pore types at the interface have been categorized, focusing on how the material contact angle variations between the current collector and electrolyte influence wetting dynamics. Notably, it is observed that higher contact angles (90°) between the electrolyte and current collector increase the risk of trapping gas. Conversely, lower angles (15° and 35°) improve overall saturation; however, the enhancement of the wetting rate is particularly noticeable when interconnected pores are present at the interfaces of the electrode and battery components. This study underscores the combined influence of the separator and current collector in comprehending electrolyte wetting behavior, thus contributing to the advancement of battery technology.

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.

drain port at the bottom center of the tank. Over time, the dimple penetrates the drain port, a free surface forms a long and slender string shape in the tank, and a so-called vortexing (air core) phenomenon occurs. The generation of a vortex core depends on the size of the tank and drain port, and on the properties of the liquid in the tank. In this study, the liquid level and the time at which the vortex core is initially generated are numerically investigated using different values of tank diameter, drain port diameter, and initial tank rotational speeds. Instead of a full three-dimensional analysis, a two-dimensional axisymmetric simulation is conducted. The momentum conservation equation in the circumferential direction is additionally solved in the two-dimensional mesh system. Several non-dimensional variables are created: the ratio of the air core generation distance and tank diameter, the diameter ratio of the tank and drain port, the rotational Reynolds number, the rotational Froude number, and the rotational Weber number. Finally, the non-dimensional air core generation distance is correlated with the other non-dimensional parameters.