The aerodynamic performance of the feathertail glider, Acrobates pygmaeus (Marsupialia: Acrobatidae)

2014 ◽  
Vol 62 (1) ◽  
pp. 80 ◽  
Author(s):  
Peter A. Pridmore ◽  
Peter H. Hoffmann
Keyword(s):  
Angle Of Attack ◽  
Aerodynamic Performance ◽  
Few Data ◽  
Steady Velocity

Photographic and videographic investigations of the aerodynamic performance of four captive adult Acrobates pygmeus are described. During short (1–4 m) glides, steep angles of descent (>45°) and large angles of attack (up to 50°) were used mid-flight, and the possums failed to achieve steady velocities. During longer (>10 m) glides steady velocities of 5.3–7.5 m s–1 were achieved, and glide angles of 21–42° and angles of attack between 36° and 45° were used. The best (lowest) glide angles used at steady velocity were similar to those documented in sugar gliders, but involved lower air speeds. During steady gliding the forelimbs of Acrobates assumed an ‘elbows-out’ disposition similar to that of Petauroides volans, and unlike that of petaurid gliders. A glide polar for Acrobates shows that it uses lower air speeds and higher sinking speeds than other gliding animals for which polars are available (several birds and one bat). Few data on the radius of turn and sinking speed were obtained; nevertheless, in accord with theory, sinking speeds were higher during tighter turns. During flight the feather-like tail was used to generate pitching movements and adjust the angle of attack and hence glide angle. However, the control of turns seems to be achieved primarily through limb adjustments.

scholarly journals Numerical simulation of flapping airfoil with alula

2020 ◽  
Vol 12 ◽  
pp. 175682932097798
Author(s):  
Han Bao ◽  
Wenqing Yang ◽  
Dongfu Ma ◽  
Wenping Song ◽  
Bifeng Song
Keyword(s):  
Aerodynamic Force ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Geometric Parameters ◽  
Flight Performance ◽  
Relative Angle ◽  
Vertical Distance ◽  
Unsteady Effect ◽  
Flapping Airfoil

Bionic micro aerial vehicles have become popular because of their high thrust efficiency and deceptive appearances. Leading edge or trailing edge devices (such as slots or flaps) are often used to improve the flight performance. Birds in nature also have leading-edge devices, known as the alula that can improve their flight performance at large angles of attack. In the present study, the aerodynamic performance of a flapping airfoil with alula is numerically simulated to illustrate the effects of different alula geometric parameters. Different alula relative angles of attack β (the angle between the chord line of the alula and that of the main airfoil) and vertical distances h between the alula and the main airfoil are simulated at pre-stall and post-stall conditions. Results show that at pre-stall condition, the lift increases with the relative angle of attack and the vertical distance, but the aerodynamic performance is degraded in the presence of alula compared with no alula, whereas at post-stall condition, the alula greatly enhances the lift. However, there seems to be an optimal relative angle of attack for the maximum lift enhancement at a fixed vertical distance considering the unsteady effect, which may indicate birds can adjust the alula twisting at different spanwise positions to achieve the best flight performance. Different alula geometric parameters may affect the aerodynamic force by modifying the pressure distribution along the airfoil. The results are instructive for design of flapping-wing bionic unmanned air vehicles.

The Effect of Belly-Flap on Aerodynamic Performance of Blended Wing Body Civil Aircraft

2013 ◽  
Vol 378 ◽  
pp. 69-73
Author(s):  
Chen Fang Cai ◽  
Yong Ming Qin ◽  
Jiang Hao Wu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Angle Of Attack ◽  
Aerodynamic Performance ◽  
Design Parameters ◽  
Flight Safety ◽  
Optimized Design ◽  
Flight Condition ◽  
Civil Aircraft ◽  
Blended Wing Body

The effect of Belly-flap on aerodynamic performance of BWB civil aircraft are investigated in take-off and landing by computational fluid dynamics. And the overload of BWB with Belly-flap also is calculated in the same flight condition. Six parameters are discussed as design parameters of the Belly flap. It is shown that the proper combination of design parameters of Belly-flap can increase the maximum of lift and reduce the angle of attack and nose down moment to improve the flight safety in take-off and landing. When the aircraft with Belly-flap encounters the gust, the maximum overload is very close to 2.5 which are requested by FAR. It is suggested the optimized design of Belly-flap should be done if the Belly-flap is applied in BWB civil aircraft.

scholarly journals An Experimental Analysis on the Effects of Stagger on the Aerodynamic Forces of Tandem Wings

AVIA ◽  
2021 ◽  
Vol 2 (2) ◽  
Author(s):  
Y Parlindungan ◽  
S Tobing
Keyword(s):  
Experimental Analysis ◽  
Numerical Study ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Aerodynamic Performance ◽  
Open Loop ◽  
Aerodynamic Forces ◽  
Subsonic Wind Tunnel ◽  
Lift And Drag ◽  
Naca 0012

This study is inspired by the flapping motion of natural flyers: insects. Many insects have two pairs of wings referred as tandem wings. Literature review indicates that the effects of tandem wing are influenced by parameters such as stagger (the stream-wise distance between the aerodynamic center of the front and the rear airfoil), angle-of-attack and flow velocity. As a first stage, this study focuses on the effects of stagger (St) on the aerodynamic performance of tandem wings. A recent numerical study of stagger on tandem airfoils in turbulent flow (Re = 6000000) concluded that a larger stagger resulted in a decrease in lift force, and an increase in drag force. However, for laminar flow (Re = 2000), increasing the stagger was not found to be detrimental for aerodynamic performance. Another work also revealed that the maximum lift coefficient for a tandem configuration decreased with increasing stagger. The focus of this study is to perform an experimental analysis of tandem two-dimensional (2D) NACA 0012 airfoils. The two airfoils are set at the same angle-of-attack of 0° to 15° with 5° interval and three variations of stagger: 1c, 1.5c and 2c. The experiments are conducted using an open-loop-subsonic wind tunnel at a Reynolds number of 170000. The effects of St on the aerodynamic forces (lift and drag) are analyzed

scholarly journals Characteristics of Separation and Induced Drag in the Use of Swept-back Wing Unmanned Aerial Vehicle

2021 ◽  
Vol 2117 (1) ◽  
pp. 012013
Author(s):  
S P Setyo Hariyadi ◽  
Sutardi ◽  
Sukahir ◽  
Jamaludin
Keyword(s):  
Lift Coefficient ◽  
Angle Of Attack ◽  
Aerodynamic Performance ◽  
Turbulent Model ◽  
Total Drag ◽  
Aircraft Wings ◽  
Pressure Drag ◽  
Induced Drag ◽  
Aerial Vehicle ◽  
Almost All

Abstract The swept-back wing has been used in almost all aircraft wings. This is necessary to reduce the pressure drag from the wings so that there is an increase in aerodynamic performance. The aerodynamic performance is the ratio between the total drag coefficient and the lift coefficient. This research attempts to explain the swept-back wing phenomenon in unmanned aerial vehicles (UAV) on Eppler 562 airfoil. The numerical simulation uses the k-ε turbulent model at Reynolds number (Re) = 2.34 x 104. Variation of backward swept angle Λ = 0°, 15°, and 30°. The separation growth Λ = 0° occurred more on the wing root, while Λ = 15° and Λ = 30° occurred more on the wingtip. At Λ = 15°, as the angle of attack increases, the area of the separation increases, and the area of the transition towards the separation decreases. The reattach area also has an increase in the area of the trailing edge. At Λ = 30°, with an increase in the angle of attack, there is a shift from the wingtip area to the mid-span. The area of separation and transition to separation has increased significantly. The re-attach area at α = 8o has not been seen, so at α = 12o it has been seen significantly. The vorticity on the x-axis shows Λ = 15°, and Λ = 30° has a wider area while on the z-axis, Λ = 15°, and Λ = 30° have stronger vortex strength. However, in the mid-span, Λ = 0° has a stronger result.

scholarly journals The Effect of Gurney Flap and Trailing-edge Wedge on the Aerodynamic Behavior of an Axial Turbine Blade

2021 ◽  
Vol 2 (4) ◽  
pp. 293-305
Author(s):  
Mohammad Mahdi Mahzoon ◽  
Masoud Kharati-Koopaee
Keyword(s):  
Angle Of Attack ◽  
Vortex Generator ◽  
Aerodynamic Performance ◽  
Trailing Edge ◽  
Blunt Trailing Edge ◽  
Gurney Flap ◽  
Maximum Increment ◽  
Lift And Drag ◽  
Lift And Drag Coefficient

In this research, the effect of Gurney flap and trailing-edge wedge on the aerodynamic behavior of blunt trailing-edge airfoil Du97-W-300 which is equipped with vortex generator is studied. To do this, the role of Gurney flap and trailing-edge wedge on the lift and drag coefficient and also aerodynamic performance of the airfoil is studied. Validation of the numerical model is performed by comparison of the obtained results with those of experiment. Results show that before stall, Gurney flap leads to the increase in the aerodynamic performance in a wider range of angle of attack. Numerical findings reveal that the maximum increment for the aerodynamic performance is obtained at low angle of attack when trailing-edge wedge is employed. It is found that for the highest considered value of Gurney flap and trailing-edge wedge heights, where the highest values for the lift occur, the higher aerodynamic performance at low angle of attack is obtained when trailing-edge wedge is used and at high angle of attack, the Gurney flap results in a higher aerodynamic performance. It is also shown that when high aerodynamic performance is concerned, addition of Gurney flap to the airfoil leads to the higher value for the lift. Doi: 10.28991/HIJ-2021-02-04-03 Full Text: PDF

Nonlinear lift increase at high angles of attack for double swept waverider

2020 ◽  
Vol 34 (14n16) ◽  
pp. 2040124
Author(s):  
Chuan-Zhen Liu ◽  
Peng Bai
Keyword(s):  
Shock Wave ◽  
Mach Number ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Lower Surface ◽  
Aerodynamic Performance ◽  
Sweep Angle ◽  
Vital Interest ◽  
High Angles Of Attack ◽  
Nonlinear Increase

The nonlinear increase of the lift of the double swept waverider at high angles of attack is of vital interest. The aerodynamic performance of the double swept waverider is calculated and compared with that of single swept waveriders. Results suggest that the lift nonlinearity of the double swept waverider is stronger than that of equal-planform-area single swept one, and the nonlinearity increases as Mach number increases. Some scholars have proposed the “vortex lift” to explain the nonlinear lift increase, but it is questionable as the main lift of the waverider comes from the lower surface rather than the upper surface. This paper proposes another explanation that the nonlinear lift increase is related to the attachment of shock wave, influenced by the leading-edge sweep angle. The shock wave is more inclined to attach under the lower surface with smaller swept than that of larger swept as angle of attack increases. When the shock wave attaches, the pressure increase via angle of attack is nonlinear, leading to the nonlinearity of lift increase.

Aerodynamic Performance and Acoustic Characteristics of Bionic Airfoil Inspired by Three-Dimensional Long-Eared Owl Wing Under Low Reynolds Number

2016 ◽  
Author(s):  
Dian Li ◽  
Xiaomin Liu
Keyword(s):  
Sound Pressure ◽  
Separation Bubble ◽  
Angle Of Attack ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Pressure Level ◽  
Aerodynamic Noise ◽  
Acoustic Characteristics ◽  
Unsteady Aerodynamic ◽  
Bionic Blade

The aerodynamic performance and noise of the blade are two important aspects which people pay much attention nowadays in the design of turbine machinery such as centrifugal fan and axial flow fan. In this paper, the three-dimensional model of the long-eared owl wing is established based on the section theory and fitting formula firstly. And then, unsteady aerodynamic and acoustic characteristics of the bionic blade are numerically investigated using Large-Eddy Simulation (LES) and the Ffowcs Williams-Hawkings (FW-H) equation based on Lighthill’s acoustic theory. The results indicate that the deeply concaved lower surface near the wing root plays a significant role in improving the lift-to-drag ratio. The lift coefficient and drag coefficient of the bionic blade is analyzed by comparing two-dimensional and three-dimensional results. The cross section profiles near the wing root possess the larger lift coefficients and the lesser drag coefficients, even than the three-dimensional long-eared owl wing. The size of the separation bubble grows at increasing angle of attack. The 40% cross-section profile of the long-eared owl wing could increase the distance between the corresponding vortex centers with wall surface thus reducing the range of the vortex shedding near the wall effectively. The iso-Q surfaces show that the location of the vortex shedding and the movement of separation bubble. When the angle of attack α is 5°, the aerodynamic noise generated by the bionic blade is lower than in other angle of attack condition. The minimum value of the sound pressure level (SPL) is even 17.9dB on the y-direction. In the range of 5°–15°, the strength and size of the vortex motion increase with the increase of the angle of attack. The far-field noise suggests the directivities of dipole noise. The range of the separation bubbles act as the most influence of the noise generation. The sound pressure level (SPL) of bionic blade at α = 5° is less than other conditions and the minimum value is even 17.9dB. The thin airfoil near the wingtip could decrease the pressure fluctuation from the blade surface that can reduce the unsteady aerodynamic noise. It means the unique structure of the long-eared owl wing can suppresses the unsteady pressure fluctuation on the surface which could decrease the noise generated by the wing surface.

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