Effect of Aerodynamic Characteristics on Micro Spike of Dragonfly Wings in Gliding Flight

1. A live laggar falcon (Falco jugger) glided in a wind tunnel at speeds between 6.6 and 15.9 m./sec. The bird had a maximum lift to drag ratio (L/D) of 10 at a speed of 12.5 m./sec. As the falcon increased its air speed at a given glide angle, it reduced its wing span, wing area and lift coefficient. 2. A model aircraft with about the same wingspan as the falcon had a maximum L/D value of 10. 3. Published measurements of the aerodynamic characteristics of gliding birds are summarized by presenting them in a diagram showing air speed, sinking speed and L/D values. Data for a high-performance sailplane are included. The soaring birds had maximum L/D values near 10, or about one quarter that of the sailplane. The birds glided more slowly than the sailplane and had about the same sinking speed. 4. The ‘equivalent parasite area’ method used by aircraft designers to estimate parasite drag was modified for use with gliding birds, and empirical data are presented to provide a means of predicting the gliding performance of a bird in the absence of wind-tunnel tests. 5. The birds in this study had conventional values for parasite drag. Technical errors seem responsible for published claims of unusually low parasite drag values in a vulture. 6. The falcon adjusted its wing span in flight to achieve nearly the maximum possible L/D value over its range of gliding speeds. 7. The maximum terminal speed of the falcon in a vertical dive is estimated to be 100 m./sec.

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Numerical Investigation on Flapping Aerodynamic Performance of Dragonfly Wings in Crosswind

International Journal of Aerospace Engineering ◽

10.1155/2020/7325154 ◽

2020 ◽

Vol 2020 ◽

pp. 1-14

Author(s):

Chao Wang ◽

Rui Zhang ◽

Chaoying Zhou ◽

Zhenzhong Sun

Keyword(s):

Stokes Equations ◽

Three Dimensional ◽

Lateral Force ◽

Aerodynamic Characteristics ◽

Navier Stokes ◽

Aerodynamic Forces ◽

Sideslip Angle ◽

Flight Direction ◽

Time Average ◽

Dragonfly Wings

Numerical simulations are performed to investigate the influence of crosswind on the aerodynamic characteristics of rigid dragonfly-like flapping wings through the solution of the three-dimensional unsteady Navier-Stokes equations. The aerodynamic forces, the moments, and the flow structures of four dragonfly wings are examined when the sideslip angle ϑ between the crosswind and the flight direction varied from 0o to 90o. The stability of the dragonfly model in crosswind is analyzed. The results show that the sideslip angle ϑ has a little effect on the total time-average lift force but significant influence on the total time-average thrust force, lateral force, and three-direction torques. An increase in the sideslip angle gives rise to a larger total time-average lateral force and yaw moment. These may accelerate the lateral skewing of the dragonfly, and the increased rolling and pitching moments will further aggravate the instability of the dragonfly model. The vorticities and reattached flow on the wings move laterally to one side due to the crosswind, and the pressure on wing surfaces is no longer symmetrical and hence, the balance between the aerodynamic forces of the wings on two sides is broken. The effects of the sideslip angle ϑ on each dragonfly wing are different, e.g., ϑ has a greater effect on the aerodynamic forces of the hind wings than those of the fore wings. When sensing a crosswind, it is optimal to control the two hind wings of the bionic dragonfly-like micro aerial vehicles.

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Aerodynamic characteristics of flying fish in gliding flight

Journal of Experimental Biology ◽

10.1242/jeb.046052 ◽

2010 ◽

Vol 213 (19) ◽

pp. 3269-3279 ◽

Cited By ~ 40

Author(s):

H. Park ◽

H. Choi

Keyword(s):

Aerodynamic Characteristics ◽

Flying Fish ◽

Gliding Flight

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Simulation Analysis of the Aerodynamic Performance of a Bionic Aircraft with Foldable Beetle Wings in Gliding Flight

Applied Bionics and Biomechanics ◽

10.1155/2020/8843360 ◽

2020 ◽

Vol 2020 ◽

pp. 1-12

Author(s):

Caidong Wang ◽

Yu Ning ◽

Xinjie Wang ◽

Junqiu Zhang ◽

Liangwen Wang

Keyword(s):

Simulation Analysis ◽

Simulation Method ◽

Aerodynamic Characteristics ◽

Aerodynamic Performance ◽

Elastic Model ◽

Flight Performance ◽

Flexible Wings ◽

Gliding Flight ◽

Drag Ratio ◽

Gliding Movement

Beetles have excellent flight performance. Based on the four-plate mechanism theory, a novel bionic flapping aircraft with foldable beetle wings was designed. It can perform flapping, gliding, wing folding, and abduction/adduction movements with a self-locking function. In order to study the flight characteristics of beetles and improve their gliding performance, this paper used a two-way Fluid-Structure Interaction (FSI) numerical simulation method to focus on the gliding performance of the bionic flapping aircraft. The effects of elastic model, rigid and flexible wing, angle of attack, and velocity on the aerodynamic characteristics of the aircraft in gliding flight are analyzed. It was found that the elastic modulus of the flexible hinges has little effect on the aerodynamic performance of the aircraft. Both the rigid and the flexible wings have a maximum lift-to-drag ratio when the attack angle is 10°. The lift increased with the increase of the gliding speed, and it was found that the lift cannot support the gliding movement at low speeds. In order to achieve gliding, considering the weight and flight performance, the weight of the microair vehicle is controlled at about 3 g, and the gliding speed is guaranteed to be greater than 6.5 m/s. The results of this study are of great significance for the design of bionic flapping aircrafts.

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Aerodynamic characteristics of the wings and body of a dragonfly

Journal of Experimental Biology ◽

10.1242/jeb.199.2.281 ◽

1996 ◽

Vol 199 (2) ◽

pp. 281-294 ◽

Cited By ~ 2

Author(s):

M Okamoto ◽

K Yasuda ◽

A Azuma

Keyword(s):

Surface Roughness ◽

Wind Tunnel ◽

Flow Field ◽

Leading Edge ◽

Reynolds Numbers ◽

Aerodynamic Characteristics ◽

Free Flight ◽

Flight Tests ◽

Dragonfly Wings ◽

Artificial Wing

The aerodynamic characteristics of the wings and body of a dragonfly and of artificial wing models were studied by conducting two types of wind-tunnel tests and a number of free-flight tests of gliders made using dragonfly wings. The results were consistent between these different tests. The effects of camber, thickness, sharpness of the leading edge and surface roughness on the aerodynamic characteristics of the wings were characterized in the flow field with Reynolds numbers (Re) as low as 103 to 104.

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