Optimal flapping wing for maximum vertical aerodynamic force in hover: twisted or flat?

Abstract

This work presents a parametric study, using the unsteady blade element theory, to investigate the role of twist in a hovering flapping wing. For the investigation, a flapping-wing system was developed to create a wing motion of large flapping amplitude. Three-dimensional kinematics of a passively twisted wing, which is capable of creating a linearly variable geometric angle of attack (AoA) along the wingspan, was measured during the flapping motion and used for the analysis. Several negative twist or wash-out configurations with different values of twist angle, which is defined as the difference in the average geometric AoAs at the wing root and the wing tip, were obtained from the measured wing kinematics through linear interpolation and extrapolation. The aerodynamic force generation and aerodynamic power consumption of these twisted wings were obtained and compared with those of flat wings. For the same aerodynamic power consumption, the vertical aerodynamic forces produced by the negatively twisted wings are approximately 10%-20% less than those produced by the flat wings. However, these twisted wings require approximately 1%-6% more power than flat wings to produce the same vertical force. In addition, the maximum-force-producing twisted wing, which was found to be the positive twist or wash-in configuration, was used for comparison with the maximum-force-producing flat wing. The results revealed that the vertical aerodynamic force and aerodynamic power consumption of the two types of wings are almost identical for the hovering condition. The power loading of the positively twisted wing is only approximately 2% higher than that of the maximum-force-producing flat wing. Thus, the flat wing with proper wing kinematics (or wing rotation) can be regarded as a simple and efficient candidate for the development of hovering flapping-wing micro air vehicle.

Wing inertia as a cause of aerodynamically uneconomical flight with high angles-of-attack in hovering insects

“…The cycleaverage horizontal force was approximately 4 mN (≈0.41 gf ), which results in a slightly backward flight of the beetle. Thus, the estimated forces are acceptable to strengthen the accuracy of force estimation by the BET model that was validated in previous papers (Truong et al, 2011;Phan et al, 2016). The power components required to flap and rotate the hindwings are shown in Fig.…”

“…We used the blade-element theory (BET) model developed in our previous work (Truong et al, 2011;Phan et al, 2016), which is based on 3D wing kinematics as the input condition, to estimate the force generation and power requirement. The force acting on each spanwise section (dr in Fig.…”

Towards Bio-Inspiration, Development, and Manufacturing of a Flapping-Wing Micro Air Vehicle

“…Many researchers are focusing on flapping-wings in an effort to improve these bio-inspired flyers and move towards bio-mimicked systems through aerodynamic investigations and actuation mechanism optimization [22][23][24]. In addition, a number of researchers have focused on the performance structure of natural and robotic flyers' wings in an effort to further optimize these bio-inspired and bio-mimicked systems [25][26][27].…”

Insights into Sensitivity of Wing Shape and Kinematic Parameters Relative to Aerodynamic Performance of Flapping Wing Nano Air Vehicles

“…The inclusion of this parameter enhances the accuracy of the model while maintaining a lower computational cost than unsteady aerodynamic models. Although some unsteady models may yield better aerodynamic performance predictions, such as Phan et al [42], Parslew et al [43] have shown that the model being used provides sufficient predictions at lower computational costs. In addition, Ghommem et al [44] have validated FlapSim predications with experimental data for a flapping wing NAV (FWNAV), as can be seen in Figure 1.…”