A Wind-Tunnel Study of Gliding Flight in the Pigeon Columba Livia

1968 ◽  
Vol 49 (3) ◽  
pp. 509-526 ◽  
Author(s):  
C. J. PENNYCUICK
Keyword(s):  
Wind Tunnel ◽  
Columba Livia ◽  
Wing Area ◽  
Total Drag ◽  
Induced Drag ◽  
Wing Profile ◽  
Gliding Flight ◽  
Lift And Drag ◽  
Wind Tunnel Study ◽  
Drag Ratio

1. A technique for training pigeons to fly in a tilting wind tunnel is described, and a method of determining lift and drag in gliding flight is explained. 2. Drag measurements were made on wingless bodies and preserved feet in supplementary experiments. The results were used to analyse the measured total drag of live pigeons into (a) body drag, (b) foot drag, (c) induced drag, and (d) wing profile drag. 3. As speed is increased, gliding pigeons drastically reduce their wing span, wing area and aspect ratio. The increased induced drag resulting from this is more than offset by a very large reduction in wing profile drag. 4. Although the lift: drag ratio is at best 5.5-6.0, changes of wing area and shape keep it near its maximum, up to speeds at least twice the minimum gliding speed.

Aerodynamics of Gliding Flight of a Black Vulture Coragyps Atratus

1970 ◽  
Vol 53 (2) ◽  
pp. 363-374 ◽  
Author(s):  
G. CHRISTIAN PARROTT
Keyword(s):  
Wind Tunnel ◽  
Wing Area ◽  
Drag Coefficients ◽  
Wing Span ◽  
Drag Forces ◽  
Gliding Flight ◽  
Black Vulture ◽  
Air Speed

1. A black vulture (mass = 1.79 kg) gliding freely in a wind tunnel adjusted its wing span and wing area as its air speed and glide angle changed from 9.9 to 16.8 m/s and from 4.8° to 7.9°, respectively. 2. The minimum sinking speed was 1.09 m/s at an air speed of 11.3 m/s. 3. The maximum ratio of lift to drag forces was 11.6 at an air speed of 13.9 m/s. 4. Parasite drag coefficients for the vulture are similar to those for conventional airfoils and do not support the contention that black vultures have unusually low values of parasite drag.

scholarly journals Control of Gliding Angle in RÜppell'S Griffon Vulture Gyps RÜppellii

1971 ◽  
Vol 55 (1) ◽  
pp. 39-46 ◽  
Author(s):  
C. J. PENNYCUICK
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
The Body ◽  
Sectional Area ◽  
Wing Area ◽  
Cross Sectional ◽  
Griffon Vulture ◽  
Speed Increase ◽  
Induced Drag ◽  
Low Speeds

1. The drag of the frozen, wingless body of a Rüppell's griffon vulture was measured in a wind tunnel with a simple drag balance. The drag coefficient with feet and neck retracted was 0.43, based on the greatest cross-sectional area of the body. 2. The drag of the body was trebled by fully lowering the feet, and more than quadrupled when the tail was lowered as well, apparently owing to separation of the flow over the back. The drag coefficient of the legs and feet, based on their frontal area, varied from 0.89 to 1.08 in different positions. 3. At low speeds the use of the feet alone should reduce the glide ratio from about 15 to 10, but the airbrake effect becomes progressively more marked at higher speeds. At lower speeds reduction of the wing area produces a greater steepening of the gliding angle, but at the expense of increasing the minimum speed. Increase of induced drag would provide a highly effective gliding angle control at very low speeds, and it is suggested that this is achieved by raising the secondary feathers, which would alter the spanwise lift distribution by transferring a greater proportion of the lift to the primaries.

The Flapping Flight of Birds

1925 ◽  
Vol 29 (179) ◽  
pp. 590-594 ◽  
Author(s):  
Gilbert T. Walker
Keyword(s):  
Wind Tunnel ◽  
Flapping Flight ◽  
Present Writer ◽  
Previous Issue ◽  
Gliding Flight ◽  
It Support ◽  
Standard Section ◽  
Lift And Drag

In connection with gliding flight enough measurements of “ lift ” and “ drag ” have been made to enable us to calculate the conditions for success of an aeroplane fitted with wings of standard sections; but no attempt has been made, as far as the present writer is aware, to ascertain what would happen if a flying machine were fitted with wings of standard section and these were flapped in a rhythmical manner. Would it support and propel itself? Several authors, including M. F. Fitzgerald and Colonel J. D. Fullerton in the previous issue of this journal, have discussed various portions of this problem; but instead of appealing to wind-tunnel determinations the latter has used such expressions as pSUV or pSUV2 for the pressure on a wing of area S, where p is the density of the air and V, U are the component velocities along and at right angles to its surface.

Gliding Flight of the Fulmar Petrel

1960 ◽  
Vol 37 (2) ◽  
pp. 330-338 ◽  
Author(s):  
C. J. PENNYCUICK
Keyword(s):  
Drag Coefficient ◽  
Power Output ◽  
Lift Coefficient ◽  
Wing Area ◽  
Drag Coefficients ◽  
Minimum Drag ◽  
Gliding Flight ◽  
Lift And Drag

1. The basis used for estimating lift and drag coefficients is explained. A method of obtaining a photograph of a bird flying at known airspeed and rate of sink is described. 2. 96% of the speed measurements fall between 22 and 65 ft./sec., the average being 40 ft./sec. 3. A maximum lift coefficient of 1.8 can be achieved. Wing area is reduced with increasing speed. 4. The feet are used as airbrakes. 5. A comparison of the minimum drag coefficient (0.06) with the maximum estimated power output of the pectoral muscles leaves only a narrow margin of power available for climbing. 6. The performance diagram gives a minimum gliding angle of 1 in 8½, and a minimum sinking speed of just under 4 ft./sec. 7. The fulmar has apparently sacrificed the ability to soar dynamically over the sea in order to be able to fly slowly and thus utilize light upcurrents at cliff faces.

scholarly journals Effect of Shroud Hole on the Force Characteristics of a Circular Cylinder

2019 ◽  
Vol 9 (1) ◽  
pp. 5929-5935
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Circular Cylinder ◽  
Drag Reduction ◽  
Air Flow ◽  
Flow Speed ◽  
Diameter Ratio ◽  
Total Drag ◽  
Lift And Drag ◽  
Force Characteristics

Characteristics of flow pass a shrouded cylinder were investigated experimentally using uniform and non-uniform hole shrouds. The experiments were performed to compare the effect of hole-uniformity of the perforated shroud on the cylinder lift and drag. The porosity for uniform hole shrouds in triangular and square configurations were set around 0.30, while that for non-uniform hole shrouds were set from 0.25 to 0.37. The diameter ratio between the shroud and the bare cylinder was set at 2.0. The experiment was performed in a wind tunnel at Reynolds Number of 9.345 x 103 based on the bare cylinder diameter and constant incoming air flow speed. Results showed that although all shrouded cylinder models reduced drag significantly in comparison to that of the bare cylinder case, the non-uniform hole shrouds were considerably effective than the uniform hole shrouds. Total drag reduction achieved by the non-uniform hole shrouds of 30% porosity was between 90-95% whereas that of uniform hole was only 55-80% at the same porosity.

scholarly journals THE EFFECTS OF ANGLE OF ATTACK, REYNOLD NUMBERS AND WINGLET STRUCTURE ON THE PERFORMANCE OF CESSNA 172 SKYHAWK

2018 ◽  
Vol 10 (1) ◽  
pp. 61
Author(s):  
Henny Pratiwi
Keyword(s):  
Wind Tunnel ◽  
Drag Force ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Balsa Wood ◽  
Wingtip Vortex ◽  
The One ◽  
Lift And Drag ◽  
Drag Ratio ◽  
Lift To Drag Ratio

This research aims to investigate the effects of angle of attack, Reynold numbers and winglet structure on the performance of Cessna 172 Skyhawk aircraft with winglets variation design. Winglets improve efficiency by diffusing the shed wingtip vortex, which reducing the drag due to lift and improving the wing’s lift over drag ratio. In this research, the specimens are the duplicated of Cesnna 172 Skyhawk wing with 1:40 ratio made of balsa wood. There are three different winglet designs that are compared with the one without winglet. The experiments are conducted in an open wind tunnel to measure the lift and drag force with Reynold numbers of 25,000 and 33,000. It can be concluded that the wings with winglets have higher lift coefficient than wing without winglet for both Reynold numbers. It was also found that all wings with winglets have higher lift-to-drag ratio than wings without winglet where the blended 45o cant angle has the highest value.

scholarly journals Gliding flight in a jackdaw: a wind tunnel study

2001 ◽  
Vol 204 (6) ◽  
pp. 1153-1166 ◽  
Author(s):  
M. Rosen ◽  
A. Hedenstrom
Keyword(s):  
Wind Tunnel ◽  
Bird Species ◽  
Wind Tunnels ◽  
Flight Performance ◽  
Forward Speed ◽  
Wing Area ◽  
Reference Length ◽  
Gliding Flight ◽  
Speed Range ◽  
Maximum Coefficient

We examined the gliding flight performance of a jackdaw Corvus monedula in a wind tunnel. The jackdaw was able to glide steadily at speeds between 6 and 11 m s(−1). The bird changed its wingspan and wing area over this speed range, and we measured the so-called glide super-polar, which is the envelope of fixed-wing glide polars over a range of forward speeds and sinking speeds. The glide super-polar was an inverted U-shape with a minimum sinking speed (V(ms)) at 7.4 m s(−1) and a speed for best glide (V(bg)) at 8.3 m s(−)). At the minimum sinking speed, the associated vertical sinking speed was 0.62 m s(−1). The relationship between the ratio of lift to drag (L:D) and airspeed showed an inverted U-shape with a maximum of 12.6 at 8.5 m s(−1). Wingspan decreased linearly with speed over the whole speed range investigated. The tail was spread extensively at low and moderate speeds; at speeds between 6 and 9 m s(−1), the tail area decreased linearly with speed, and at speeds above 9 m s(−1) the tail was fully furled. Reynolds number calculated with the mean chord as the reference length ranged from 38 000 to 76 000 over the speed range 6–11 m s(−1). Comparisons of the jackdaw flight performance were made with existing theory of gliding flight. We also re-analysed data on span ratios with respect to speed in two other bird species previously studied in wind tunnels. These data indicate that an equation for calculating the span ratio, which minimises the sum of induced and profile drag, does not predict the actual span ratios observed in these birds. We derive an alternative equation on the basis of the observed span ratios for calculating wingspan and wing area with respect to forward speed in gliding birds from information about body mass, maximum wingspan, maximum wing area and maximum coefficient of lift. These alternative equations can be used in combination with any model of gliding flight where wing area and wingspan are considered to calculate sinking rate with respect to forward speed.

scholarly journals A Parametric Study of Trailing Edge Flap Implementation on Three Different Airfoils Through an Artificial Neuronal Network

Symmetry ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 828
Author(s):  
Igor Rodriguez-Eguia ◽  
Iñigo Errasti ◽  
Unai Fernandez-Gamiz ◽  
Jesús María Blanco ◽  
Ekaitz Zulueta ◽  
...  
Keyword(s):  
Aerodynamic Coefficients ◽  
Trailing Edge ◽  
High Lift ◽  
Trailing Edge Flaps ◽  
Artificial Neural Network Ann ◽  
Lift And Drag ◽  
Artificial Neuronal Network ◽  
Naca 0012 ◽  
Drag Ratio ◽  
Lift To Drag Ratio

Trailing edge flaps (TEFs) are high-lift devices that generate changes in the lift and drag coefficients of an airfoil. A large number of 2D simulations are performed in this study, in order to measure these changes in aerodynamic coefficients and to analyze them for a given Reynolds number. Three different airfoils, namely NACA 0012, NACA 64(3)-618, and S810, are studied in relation to three combinations of the following parameters: angle of attack, flap angle (deflection), and flaplength. Results are in concordance with the aerodynamic results expected when studying a TEF on an airfoil, showing the effect exerted by the three parameters on both aerodynamic coefficients lift and drag. Depending on whether the airfoil flap is deployed on either the pressure zone or the suction zone, the lift-to-drag ratio, CL/CD, will increase or decrease, respectively. Besides, the use of a larger flap length will increase the higher values and decrease the lower values of the CL/CD ratio. In addition, an artificial neural network (ANN) based prediction model for aerodynamic forces was built through the results obtained from the research.

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