Size effect in insect flight: leading-edge vortex, trailing-edge vortex and tip vortex

2006 ◽  
Vol 39 ◽  
pp. S356-S357 ◽  
Author(s):  
H. Liu ◽  
H. Aono ◽  
Y. Inada ◽  
W. Shyy
Keyword(s):  
Size Effect ◽  
Insect Flight ◽  
Leading Edge ◽  
Tip Vortex ◽  
Trailing Edge ◽  
Leading Edge Vortex ◽  
Edge Vortex

scholarly journals UNSTEADY AERODYNAMIC PERFORMANCE OF MODEL WINGS AT LOW REYNOLDS NUMBERS

1993 ◽  
Vol 174 (1) ◽  
pp. 45-64 ◽  
Author(s):  
M. H. Dickinson ◽  
K. G. Gotz
Keyword(s):  
Insect Flight ◽  
Delta Wing ◽  
Force Production ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Aerodynamic Forces ◽  
Trailing Edge ◽  
Leading Edge Vortex ◽  
Precise Knowledge ◽  
Edge Vortex

The synthesis of a comprehensive theory of force production in insect flight is hindered in part by the lack of precise knowledge of unsteady forces produced by wings. Data are especially sparse in the intermediate Reynolds number regime (10<Re<1000) appropriate for the flight of small insects. This paper attempts to fill this deficit by quantifying the time-dependence of aerodynamic forces for a simple yet important motion, rapid acceleration from rest to a constant velocity at a fixed angle of attack. The study couples the measurement of lift and drag on a two-dimensional model with simultaneous flow visualization. The results of these experiments are summarized below. 1. At angles of attack below 13.5°, there was virtually no evidence of a delay in the generation of lift, in contrast to similar studies made at higher Reynolds numbers. 2. At angles of attack above 13.5°, impulsive movement resulted in the production of a leading edge vortex that stayed attached to the wing for the first 2 chord lengths of travel, resulting in an 80 % increase in lift compared to the performance measured 5 chord lengths later. It is argued that this increase is due to the process of detached vortex lift, analogous to the method of force production in delta-wing aircraft. 3. As the initial leading edge vortex is shed from the wing, a second vortex of opposite vorticity develops from the trailing edge of the wing, correlating with a decrease in lift production. This pattern of alternating leading and trailing edge vortices generates a von Karman street, which is stable for at least 7.5 chord lengths of travel. 4. Throughout the first 7.5 chords of travel the model wing exhibits a broad lift plateau at angles of attack up to 54°, which is not significantly altered by the addition of wing camber or surface projections. 5. Taken together, these results indicate how the unsteady process of vortex generation at large angles of attack might contribute to the production of aerodynamic forces in insect flight. Because the fly wing typically moves only 2–4 chord lengths each half-stroke, the complex dynamic behavior of impulsively started wing profiles is more appropriate for models of insect flight than are steady-state approximations.

The aerodynamics of revolving wings I. Model hawkmoth wings

2002 ◽  
Vol 205 (11) ◽  
pp. 1547-1564 ◽  
Author(s):  
James R. Usherwood ◽  
Charles P. Ellington
Keyword(s):  
Insect Flight ◽  
Leading Edge ◽  
Dynamic Stall ◽  
Leading Edge Vortex ◽  
Force Coefficients ◽  
Attached Flow ◽  
Edge Vortex ◽  
Drag And Lift ◽  
Geometric Relationship ◽  
Spanwise Flow

SUMMARYRecent work on flapping hawkmoth models has demonstrated the importance of a spiral `leading-edge vortex' created by dynamic stall, and maintained by some aspect of spanwise flow, for creating the lift required during flight. This study uses propeller models to investigate further the forces acting on model hawkmoth wings in `propeller-like' rotation (`revolution'). Steadily revolving model hawkmoth wings produce high vertical (≈ lift) and horizontal (≈ profile drag) force coefficients because of the presence of a leading-edge vortex. Both horizontal and vertical forces, at relevant angles of attack, are dominated by the pressure difference between the upper and lower surfaces; separation at the leading edge prevents `leading-edge suction'. This allows a simple geometric relationship between vertical and horizontal forces and the geometric angle of attack to be derived for thin, flat wings. Force coefficients are remarkably unaffected by considerable variations in leading-edge detail, twist and camber. Traditional accounts of the adaptive functions of twist and camber are based on conventional attached-flow aerodynamics and are not supported. Attempts to derive conventional profile drag and lift coefficients from `steady' propeller coefficients are relatively successful for angles of incidence up to 50° and, hence, for the angles normally applicable to insect flight.

Control of Leading-Edge Vortex Breakdown by Trailing Edge Injection

2002 ◽  
Vol 39 (2) ◽  
pp. 221-226 ◽  
Author(s):  
Anthony M. Mitchell ◽  
Didier Barberis ◽  
Pascal Molton ◽  
Jean Delery
Keyword(s):  
Vortex Breakdown ◽  
Leading Edge ◽  
Trailing Edge ◽  
Leading Edge Vortex ◽  
Edge Vortex

The Impact of Leakage Flow Tangential Velocity on Secondary Losses in a Shrouded Compressor Cascade

2012 ◽  
Author(s):  
J. W. Kim ◽  
J. S. Lee ◽  
S. J. Song ◽  
T. Kim ◽  
H-. W. Shin
Keyword(s):  
Secondary Flow ◽  
Tangential Velocity ◽  
Leading Edge ◽  
Suction Side ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
Trailing Edge ◽  
Leading Edge Vortex ◽  
Edge Vortex ◽  
The Impact

Experimental and numerical studies have been performed to investigate the effects of the leakage flow tangential velocity on the secondary flow and aerodynamic loss in an axial compressor cascade with a labyrinth seal. Six selected leakage flow tangential (vy/Uhub = 0.15, 0.25, 0.35, 0.45, 0.55 and 0.65) have been tested. In addition to the classical “secondary” flow, shroud trailing edge vortex and shroud leading edge vortex are examined. The overall loss decreases with increasing leakage flow tangential velocity. Increased leakage flow tangential velocity underturns the hub endwall flows through the blade passage, weakening the suction side hub corner separation. Due to the suction effect of the downstream cavity, increasing leakage flow tangential velocity weakens the shroud trailing edge vortex. Also, increasing leakage flow tangential velocity strengthens the shroud leading edge vortex, weakening the pressure side leg of the horseshoe vortex, and, in turn, the passage vortex. Thus, the overall loss is reduced with increasing leakage flow tangential velocity.

scholarly journals Numerical Investigation of a Dynamic Stall on a Single Rotating Blade

Aerospace ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 90
Author(s):  
Yin Ruan ◽  
Manfred Hajek
Keyword(s):  
Numerical Investigation ◽  
Vortex Structure ◽  
Leading Edge ◽  
Rotor Blades ◽  
Tip Vortex ◽  
Dynamic Stall ◽  
Leading Edge Vortex ◽  
Pitching Airfoil ◽  
Edge Vortex ◽  
High Reynolds

Dynamic stall is a phenomenon on the retreating blade of a helicopter which can lead to excessive control loads. In order to understand dynamic stall and fill the gap between the investigations on pitching wings and full helicopter rotor blades, a numerical investigation of a single rotating and pitching blade is carried out. The flow phenomena thereupon including the Ω-shaped dynamic stall vortex, the interaction of the leading edge vortex with the tip vortex, and a newly noticed vortex structure originating inboard are examined; they show similarities to pitching wings, while also possessing their unique features of a rotating system. The leading edge/tip vortex interaction dominates the post-stall stage. A newly noticed swell structure is observed to have a great impact on the load in the post-stall stage. With such a high Reynolds number, the Coriolis force exerted on the leading edge vortex is negligible compared to the pressure force. The force history/vortex structure of the slice r/R = 0.898 is compared with a 2D pitching airfoil with the same harmonic pitch motion, and the current simulation shows the important role played by the swell structure in the recovery stage.

A Study of the Leading Edge Vortex and Tip Vortex on Prop-Fan Blades

1987 ◽  
Vol 109 (3) ◽  
pp. 325-331 ◽  
Author(s):  
C. M. Vaczy ◽  
D. C. McCormick
Keyword(s):  
Flow Visualization ◽  
Systematic Study ◽  
Leading Edge ◽  
Lower Surface ◽  
Tip Vortex ◽  
Leading Edge Vortex ◽  
Edge Loading ◽  
Oil Flow ◽  
Oil Flow Visualization ◽  
Edge Vortex

An oil flow visualization study was conducted on the blades of a counterrotating prop-fan model, the CRP-X1. A kink in the oil streaks was interpreted as an indication of the leading edge vortex reattachment line. The leading edge vortex was found to be on the lower surface for cases with negative leading edge loading and on the upper surface for cases with positive leading edge loading. For most cases, the leading edge vortex merged with a tip vortex. The results presented here represent the first systematic study of this phenomenon.

Trailing edge flap influence on leading edge vortex flap aerodynamics

1983 ◽  
Vol 20 (2) ◽  
pp. 165-169 ◽  
Author(s):  
Arthur C. Grantz ◽  
J. F. Marchman
Keyword(s):  
Leading Edge ◽  
Trailing Edge ◽  
Leading Edge Vortex ◽  
Edge Vortex ◽  
Trailing Edge Flap

scholarly journals The three–dimensional leading–edge vortex of a ‘hovering’ model hawkmoth

1997 ◽  
Vol 352 (1351) ◽  
pp. 329-340 ◽  
Author(s):  
Coen van den Berg ◽  
Charles P. Ellington
Keyword(s):  
Wing Length ◽  
Three Dimensional ◽  
Axial Flow ◽  
Leading Edge ◽  
Tip Vortex ◽  
Flow Visualisation ◽  
High Lift ◽  
Leading Edge Vortex ◽  
Edge Vortex ◽  
Wing Chord

Recent flow visualisation experiments with the hawkmoth, Manduca sexta , revealed small but clear leading–edge vortex and a pronounced three–dimensional flow. Details of this flow pattern were studied with a scaled–up, robotic insect (‘the flapper’) that accurately mimicked the wing movements of a hovering hawkmoth. Smoke released from the leading edge of the flapper wing confirmed the existence of a small, strong and stable leading–edge vortex, increasing in size from wingbase to wingtip. Between 25 and 75 % of the wing length, its diameter increased approximately from 10 to 50 % of the wing chord. The leading–edge vortex had a strong axial flow veolocity, which stabilized it and reduced its diamater. The vortex separated from the wing at approximately 75 % of the wing length and thus fed vorticity into a large, tangled tip vortex. If the circulation of the leading–edge vortex were fully used for lift generation, it could support up to two–thirds of the hawkmoth's weight during the downstroke. The growth of this circulation with time and spanwise position clearly identify dynamic stall as the unsteady aerodynamic mechanism responsible for high lift production by hovering hawkmoths and possibly also by many other insect species.

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