Many developments in aerospace science have originated from nature. One of these developments has been obtained through inspirations from flying locomotion. The aim of this study is to simulate the flapping mechanism of the black-headed gull in forward flight. The wing of the black-headed gull is characterized entirely by complex dihedral, dividing the wing into two distinct parts. Hence, a flapping mechanism with different bending deflection angles is constructed and compared with a primitive flapping mechanism. Firstly, parametric studies are conducted to assess the role of flapping frequency, velocity and bending deflection angle on the lift, thrust and power loading of the membrane flexible wing at 10 ° angle of attack. Secondly, dimensional analysis is used to establish the similarity between the real gull and the constructed mechanism. Superiority of the bending deflection mechanism is concluded in forward flight against simple flapping wing in terms of aerodynamic forces as well as power loading parameter. It is found that although the aerodynamic coefficients decrease with increase in advance ratio, the best power loading of the black-headed gull is obtained between advance ratio of 2 and 3, in the gull's aerodynamically quasi-steady regime.

Sinusoidal leading-edge wings have shown a high performance after the stall region. In this study, the role of smart flaps in the aerodynamics of smooth and sinusoidal leading-edge wings at low Reynolds numbers of 29,000, 40,000 and 58,000 is investigated. Four wings with NACA 634-021 profile are firstly designed and then manufactured by a 3 D printer. Beam bending equation is used to determine the smart flap chord deflection. Next, wind tunnel tests are carried out to measure the lift and drag forces of proposed wings for a wide range of angles of attack, from zero to 36 degrees. Results show that using trailing-edge smart flap in sinusoidal leading-edge wing delays the stall point compared to the same wing without flap. However, a combination of smooth leading-edge wing and smart flap advances the stall. Furthermore, it is found that wings with smart flap generally have a higher lift to drag ratio due to their excellent performance in producing lift.

Scientists have been improving the aerodynamic performance of flapping micro aerial vehicles by drawing inspiration from birds and insect flight. In this research study, first, the flapping mechanism of the black-headed gull is designed and then it is constructed in order to investigate the effects of wing bending deflection on the aerodynamic performance. Thrust generation, power consumption and power loading are considered as performance parameters. Three wings representing different underlying structures, namely flexible membrane, rigid membrane and airfoil, are fabricated with the same planform to investigate the roles of flexibility, thickness and camber. Experiments are performed for flapping frequencies ranging from 1.5 Hz to 6 Hz, 10 degrees angle of attack and no wind tunnel velocity (hovering flight). The results indicate that the aerodynamic performance is improved by using the bending deflection mechanism in comparison with the simple flapping mechanism. Moreover, we can conclude that the performance of the airfoil wing is superior to flexible and rigid wings.

Sinusoidal leading-edge wings have attracted many considerations since they can delay the stall and enhance the maneuverability. The main contribution of this research study is to experimentally investigate effects of ground on aerodynamic performance of sinusoidal leading-edge wings. To this end, 6 tubercled wings with different amplitudes and wavelengths are fabricated and compared with the baseline wing which has smooth leading-edge. Proposed wings are tested in different distances from the ground in a wind tunnel lab for a wide range of angle of attack from 0° to 36° and low Reynolds number of 45,000. Results indicated that lift coefficient is improved when wings get close to the ground. Furthermore, increment of protuberance amplitude in the vicinity of the ground could efficiently prevent stalling particularly for shorter wavelength.

Present study experimentally investigates the effects of ground clearance and Reynolds number on aerodynamic coefficients of smooth and sinusoidal leading-edge wings. Wind tunnel tests are conducted over a wide range of angles of attack from zero to 36 degrees, low Reynolds numbers of 30,000, 45,000 and 60,000, and also ground clearances of 0.5, 1 and ∞. Results showed that reduction of ground clearance and increment of Reynolds number cause the lift coefficient and the lift to drag ratio of both wings to be enhanced. Furthermore, the effects of Reynolds number and ground clearance on the smooth leading-edge wing are more than the sinusoidal leading-edge one. In addition, the sinusoidal leading-edge wing shows an excellent performance in the poststall region due to producing a higher lift and also by delaying the stall angle compared to the smooth leading-edge wing.