Gliding Flight of the Dog-Faced Bat Rousettus Aegyptiacus Observed in a Wind Tunnel

1971 ◽  
Vol 55 (3) ◽  
pp. 833-845 ◽  
Author(s):  
C. J. PENNYCUICK
Keyword(s):  
Wind Tunnel ◽  
Lift Coefficient ◽  
Trailing Edge ◽  
Number Range ◽  
High Speeds ◽  
Gliding Flight ◽  
Speed Range ◽  
Simple Regression Analysis ◽  
Drag Analysis ◽  
Very High

1. A bat was trained to fly in a tilting wind tunnel. Stereoscopic photographs were taken, both by reflected and by transmitted light, and measurements of best gliding angle were made. 2. Variation of wing span and area at different speeds was much less than in birds. This is attributed to the construction of the wing, which prevents the bat from folding back the manus in flight, because this would lead to collapse of the plagiopatagium. 3. The trailing edge of the wing is normally deflected upwards in flight, at least in the distal parts. This is interpreted as providing longitudinal stability. The plagiopatagialis proprii muscles appear to act as an elevator, by deflecting the trailing edge of the plagiopatagium upwards. 4. The speed range over which the bat could glide was 5·3-11·0 m/s. Its maximum lift coefficient was 1·5, and its best glide ratio 6·8:1. The Reynolds number range, based on mean chord, was 3·26 x 104 to 6·79 x 104. 5. A simple regression analysis of the glide polar indicated a very high span efficiency factor (k) and low wing profile drag coefficient (Cdp). On the other hand, a drag analysis on the assumption that k = 1 leads to an improbably large increase in the estimated Cdp at low speeds. It is suggested that the correct interpretation probably lies between these extremes, with k ≊ 1·5; Cdp would then be about 0·02 at high speeds, rising to somewhat over 0·1 at the minimum speed. 6. It would appear that the bat is not so good as a pigeon at fast gliding, but better at low-speed manoeuvring. On most points of performance, however, the two are remarkably similar.

Aerodynamics of Gliding Flight in a Falcon and Other Birds

1970 ◽  
Vol 52 (2) ◽  
pp. 345-367 ◽  
Author(s):  
VANCE A. TUCKER ◽  
G. CHRISTIAN PARROTT
Keyword(s):  
Wind Tunnel ◽  
High Performance ◽  
Lift Coefficient ◽  
Aerodynamic Characteristics ◽  
Wing Span ◽  
Technical Errors ◽  
Gliding Flight ◽  
Air Speed ◽  
D Values ◽  
D Value

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.

scholarly journals Design and Validation of a New Morphing Camber System by Testing in the Price—Païdoussis Subsonic Wind Tunnel

Aerospace ◽  
2020 ◽  
Vol 7 (3) ◽  
pp. 23 ◽  
Author(s):  
David Communier ◽  
Ruxandra Mihaela Botez ◽  
Tony Wong
Keyword(s):  
Wind Tunnel ◽  
Unmanned Aerial Vehicle ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Trailing Edge ◽  
Subsonic Wind Tunnel ◽  
Aerial Vehicle ◽  
Stall Angle

This paper presents the design and wind tunnel testing of a morphing camber system and an estimation of performances on an unmanned aerial vehicle. The morphing camber system is a combination of two subsystems: the morphing trailing edge and the morphing leading edge. Results of the present study show that the aerodynamics effects of the two subsystems are combined, without interfering with each other on the wing. The morphing camber system acts only on the lift coefficient at a 0° angle of attack when morphing the trailing edge, and only on the stall angle when morphing the leading edge. The behavior of the aerodynamics performances from the MTE and the MLE should allow individual control of the morphing camber trailing and leading edges. The estimation of the performances of the morphing camber on an unmanned aerial vehicle indicates that the morphing of the camber allows a drag reduction. This result is due to the smaller angle of attack needed for an unmanned aerial vehicle equipped with the morphing camber system than an unmanned aerial vehicle equipped with classical aileron. In the case study, the morphing camber system was found to allow a reduction of the drag when the lift coefficient was higher than 0.48.

Drag and lift measurements of solid sports balls in still air

2017 ◽  
Vol 232 (3) ◽  
pp. 255-263 ◽  
Author(s):  
Jeff R Kensrud ◽  
Lloyd V Smith
Keyword(s):  
Surface Roughness ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Rough Surface ◽  
Lift Coefficient ◽  
Laboratory Setting ◽  
Air Drag ◽  
High Speeds ◽  
Drag And Lift ◽  
Lift And Drag

The following article considers lift and drag measurements of solid sports balls propelled through still air in a laboratory setting. The balls traveled at speeds ranging from 26 to 134 m/s with spin rates up to 3900 r/min. Light gates measured the speed and location of the balls at two locations from which lift and drag values were determined. Ball roughness varied from polished to rough surface protrusions, that is, seams as high as 1.5 mm. Lift and drag were observed to depend on speed, spin rate, surface roughness, and seam orientation. A drag crisis was observed on smooth balls as well as non-rotating seamed balls with seam heights less than 0.9 mm. The drag coefficient of approximately 0.42 was nearly constant with speed for spinning seamed balls with seam height greater than 0.9 mm. The still air drag coefficient of smooth balls was comparable to wind tunnel drag at low speeds ( Re < 2 × 105) and higher than wind tunnel results at high speeds ( Re > 2 × 105). The lift and drag coefficients of spinning balls increased with increasing spin rate. The lift coefficient of baseballs was not sensitive to ball orientation or seam height.

AERODYNAMICS OF GLIDING FLIGHT IN A HARRIS' HAWK, PARABUTEO UNICINCTUS

1990 ◽  
Vol 149 (1) ◽  
pp. 469-489 ◽  
Author(s):  
VANCE A. TUCKER ◽  
CARLTON HEINE
Keyword(s):  
Wind Tunnel ◽  
Lift Coefficient ◽  
Drag Coefficients ◽  
Polar Curve ◽  
Wing Span ◽  
Gliding Flight ◽  
Black Vulture ◽  
Polar Area ◽  
Air Speed ◽  
Parabuteo Unicinctus

1. A Harris' hawk with a mass of 0.702 kg and a maximum wing span of 1.02 m glided freely in a wind tunnel at air speeds between 6.1 and 16.2ms−1. The glide angle varied from 8.5% at the slowest speed to a minimum of 5% at speeds between 8.0 and 14.7 ms−1. The maximum ratio of lift to drag was 10.9 and the minimum sinking speed was 0.81ms−1 2. Wing span decreased when either air speed or glide angle increased. Wing area was a parabolic function of wing span 3. Lift and profile drag coefficients of the wings fell in a polar area similar to that for a laggar falcon (Falco jugger) and a black vulture (Coragyps atratus). A single polar curve relating lift coefficients to minimum profile drag coefficients can predict the maximum gliding performance of all three birds when used with a mathematical model for gliding flight 4. The parasite drag values that have been used with the model are probably too high. Thus, the profile drag coefficients determined from the polar curve mentioned above are too low, and the predicted wing spans for gliding at maximum performance are too large. The predicted curve for maximum gliding performance is relatively unaffected 5. The maximum lift coefficient for the Harris' hawk in the wind tunnel was 1.6. This value is probably less than the maximum attainable, since the hawk's wings never appeared to stall. The best estimate of the minimum profile drag coefficient is 0.026 at a lift coefficient of 0.60.

A Piezocomposite Trailing-Edge for Subsonic Aircraft

2018 ◽  
Author(s):  
Cody Wright ◽  
Onur Bilgen
Keyword(s):  
Lift Coefficient ◽  
Interaction Model ◽  
Leading Edge ◽  
Unmanned Aircraft ◽  
Design Parameters ◽  
Stream Velocity ◽  
Substrate Thickness ◽  
Trailing Edge ◽  
Number Range ◽  
Reynold’S Number

This paper examines the feasibility of piezocomposite morphing airfoils and trailing edge control surfaces subjected to large dynamic pressures. Piezocomposite airfoils have been shown to be feasible on small unmanned aerial vehicles, subject to relatively low dynamic pressures, operating in the Reynold’s number range of 50k to 250k. The operating range of interest in this paper has a cruising Reynold’s number range between 250k and 1M subject to relatively large wing loading. This range of Reynold’s numbers has not been explored in detail due to the large aerodynamic loads produced. Based on the authors’ previous research on small unmanned aircraft, the proposed concept is a variable-camber airfoil that employs a continuous inextensible surface and surface-bonded piezocomposite actuators. To achieve camber-morphing, multiple piezocomposite actuating elements are applied to the upper and lower surfaces. A case study is performed to determine the design parameters of the airfoil. The parameters to be varied include the substrate thickness of the baseline airfoil, leading edge, and piezocomposite bonded areas. In addition, the positions of the piezocomposites are varied. The analysis is performed using a coupled fluid-structure interaction model assuming static aeroelastic behavior. A voltage sweep is conducted on each airfoil design while being subjected to 70 m/s free stream velocity. The sweep examines the lift coefficient and lift-to-drag ratio of the airfoil over the full operational range. This research lays the groundwork for determining the feasibility of piezocomposite morphing airfoil and trailing edge concepts for use in applications subject to large dynamic pressures.

The collection of aerosol droplets by resting tsetse flies, Glossina morsitans Westwood (Diptera: Glossinidae)

1989 ◽  
Vol 79 (4) ◽  
pp. 613-623 ◽  
Author(s):  
D. R. Johnstone ◽  
J. F. Cooper ◽  
H. M. Dobson ◽  
C. R. Turner
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Collection Efficiency ◽  
Natural Habitat ◽  
Control Measures ◽  
Tsetse Flies ◽  
Glossina Morsitans ◽  
Speed Range ◽  
Low Speed Wind Tunnel ◽  
Very High

AbstractInsecticidal aerosols dispersed from aircraft are used in control measures against Glossina spp., and the interpretation of spray monitoring data in terms of the likely effect on the flies requires some knowledge of variation of the collection efficiency of the flies under a range of appropriate conditions. A low speed wind tunnel was used to measure the collection efficiencies of the various component parts of an adult of G. morsitans Westwood when at rest on cylinders simulating the branches and twigs of the natural habitat. The wind speed range was from 0·25 to 1·5 m/s and monodisperse droplets 10, 15, 20 and 25 μm in diameter were used. Although certain body zones exhibited very high apparent collection efficiencies (primarily due to interception), the average overall efficiencies varied from as low as 0·8% for 10-μm droplets at 0·25 m/s up to 22% for 25-μm droplets at 1·5 m/s.

scholarly journals Aerodynamic analysis of aircraft model using indigenously developed wind tunnel facility

2021 ◽  
Vol 1206 (1) ◽  
pp. 012013
Author(s):  
D Makhija ◽  
S V Jain ◽  
A M Achari ◽  
K Ghosh
Keyword(s):  
Wind Tunnel ◽  
Lift Force ◽  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Angle Of Attack ◽  
Open Circuit ◽  
Force Balance ◽  
Number Range ◽  
Aircraft Model ◽  
Wide Range

Abstract This paper presents a design of force balance setup that can measure lift force acting on the aircraft model. The setup was developed indigenously and installed in an open circuit low-speed wind tunnel. It mainly consists of two components viz. a traverse mechanism that can hold the model in the test section at different angles of attack and air speeds and a supporting frame to hold the traverse mechanism over it. The spring balances are used to obtain lift force readings at different angles and air speeds. The experimental and numerical investigations were done in the wide range of Reynolds number (range: 0.55 to 1.12 lakh) and angle of attack (range: -6° to 20°). The results are presented in terms of pressure contours, velocity contours, pressure coefficient and lift coefficient. From the experiments it was found that value of lift coefficient increases with angle of attack and stalling occurs at 18° for all the air speeds. However, in the numerical results the stalling was observed little earlier than 18° angle of attack. The experimental results were compared with CFD results and an average relative error of 18% was observed which may be due to assumption of 2-D airfoil in CFD analysis.

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.

Experimental investigations of flow over NACA airfoils 0021 and 4412 of wind turbine blades with and without Tubercles

2021 ◽  
pp. 0309524X2110071
Author(s):  
Usman Butt ◽  
Shafqat Hussain ◽  
Stephan Schacht ◽  
Uwe Ritschel
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
Wind Turbine ◽  
Critical Region ◽  
Lift Coefficient ◽  
Turbine Blades ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Experimental Investigations ◽  
Wind Turbine Blades

Experimental investigations of wind turbine blades having NACA airfoils 0021 and 4412 with and without tubercles on the leading edge have been performed in a wind tunnel. It was found that the lift coefficient of the airfoil 0021 with tubercles was higher at Re = 1.2×105 and 1.69×105 in post critical region (at higher angle of attach) than airfoils without tubercles but this difference relatively diminished at higher Reynolds numbers and beyond indicating that there is no effect on the lift coefficients of airfoils with tubercles at higher Reynolds numbers whereas drag coefficient remains unchanged. It is noted that at Re = 1.69×105, the lift coefficient of airfoil without tubercles drops from 0.96 to 0.42 as the angle of attack increases from 15° to 20° which is about 56% and the corresponding values of lift coefficient for airfoil with tubercles are 0.86 and 0.7 at respective angles with18% drop.

Auto and Cross Correlation Measurements in a Turbine Cascade Using a Digital Correlator

1982 ◽  
Author(s):  
P. J. Bryanston-Cross ◽  
J. J. Camus
Keyword(s):  
Mach Number ◽  
High Speed ◽  
Cross Correlation ◽  
Turbine Blades ◽  
Image Plane ◽  
Strongly Correlated ◽  
Trailing Edge ◽  
Number Range ◽  
Cross Correlations ◽  
Digital Correlator

A simple technique has been developed which samples the dynamic image plane information of a schlieren system using a digital correlator. Measurements have been made in the passages and in the wakes of transonic turbine blades in a linear cascade. The wind tunnel runs continuously and has independently variable Reynolds and Mach number. As expected, strongly correlated vortices were found in the wake and trailing edge region at 50 KHz. Although these are strongly coherent we show that there is only limited cross-correlation from wake to wake over a Mach no. range M = 0.5 to 1.25 and variation of Reynolds number from 3 × 105 to 106. The trailing edge fluctuation cross correlations were extended both upstream and downstream and preliminary measurements indicate that this technique can be used to obtain information on wake velocity. The vortex frequency has also been measured over the same Mach number range for two different cascades. The results have been compared with high speed schlieren photographs.

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