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.

Errata: In-Flight Flow Visualization of F-106B Leading-Edge Vortex Using the Vapor-Screen Technique

1988 ◽  
Vol 25 (5) ◽  
pp. 480-480
Author(s):  
J. E. Lamar ◽  
R. A. Bruce ◽  
J. D. Pride ◽  
R. H. Smith ◽  
P. W. Brown ◽  
...  
Keyword(s):  
Flow Visualization ◽  
Leading Edge ◽  
Leading Edge Vortex ◽  
Edge Vortex

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.

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.

In-flight flow visualization of F-106B leading-edge vortex using thevapor-screen technique

1988 ◽  
Vol 25 (2) ◽  
pp. 113-120 ◽  
Author(s):  
J. E. Lamar ◽  
R. A. Bruce ◽  
J. D. Pride ◽  
R. H. Smith ◽  
P. W. Brown ◽  
...  
Keyword(s):  
Flow Visualization ◽  
Leading Edge ◽  
Leading Edge Vortex ◽  
Edge Vortex

scholarly journals Leading-Edge Vortex Characteristics of Low-Aspect-Ratio Sweptback Plates at Low Reynolds Number

2021 ◽  
Vol 11 (6) ◽  
pp. 2450
Author(s):  
Jong-Seob Han ◽  
Christian Breitsamter
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Leading Edge ◽  
Flapping Wing ◽  
Flat Plates ◽  
Leading Edge Vortex ◽  
Low Aspect Ratio ◽  
Aspect Ratios ◽  
Oil Flow ◽  
Edge Vortex

A sweptback angle can directly regulate a leading-edge vortex on various aerodynamic devices as well as on the wings of biological flyers, but the effect of a sweptback angle has not yet been sufficiently investigated. Here, we thoroughly investigated the effect of the sweptback angle on aerodynamic characteristics of low-aspect-ratio flat plates at a Reynolds number of 2.85 × 104. Direct force/moment measurements and surface oil-flow visualizations were conducted in the wind-tunnel B at the Technical University of Munich. It was found that while the maximum lift at an aspect ratio of 2.03 remains unchanged, two other aspect ratios of 3.13 and 4.50 show a gradual increment in the maximum lift with an increasing sweptback angle. The largest leading-edge vortex contribution was found at the aspect ratio of 3.13, resulting in a superior lift production at a sufficient sweptback angle. This is similar to that of a revolving/flapping wing, where an aspect ratio around three shows a superior lift production. In the oil-flow patterns, it was observed that while the leading-edge vortices at aspect ratios of 2.03 and 3.13 fully covered the surfaces, the vortex at an aspect ratio of 4.50 only covered up the surface approximately three times the chord, similar to that of a revolving/flapping wing. Based on the pattern at the aspect ratio of 4.50, a critical length of the leading-edge vortex of a sweptback plate was measured as ~3.1 times the chord.

scholarly journals The vortex wake of a ‘hovering’ model hawkmoth

1997 ◽  
Vol 352 (1351) ◽  
pp. 317-328 ◽  
Author(s):  
Coen van den Berg ◽  
Charles P. Ellington
Keyword(s):  
Lift Force ◽  
Three Dimensional ◽  
Axial Flow ◽  
Leading Edge ◽  
The Body ◽  
Tip Vortex ◽  
Vortex Rings ◽  
Leading Edge Vortex ◽  
Edge Vortex ◽  
Visualization Experiments

Visualization experiments with Manduca sexta have revealed the presence of a leading–edge vortex and a highly three–dimensional flow pattern. To further investigate this important discovery, a scaled–up robotic insect was built (the ‘flapper’) which could mimic the complex movements of the wings of a hovering hawkmoth. Smoke released from the leading edge of the flapper wing revealed a small but strong leading–edge vortex on the downstroke. This vortex had a high axial flow velocity and was stable, separating from the wing at approximately 75 % of the wing length. It connected to a large, tangled tip vortex, extending back to a combining stopping and starting vortex from pronation. At the end of the downstroke, the wake could be approximated as one vortex ring per wing. Based on the size and velocity of the vortex rings, the mean lift force during the downstroke was estimated to be about 1.5 times the body weight of a hawkmoth, confirming that the downstroke is the main provider of lift force.

In-flight flow visualization of F-106B leading-edge vortex using thevapor-screen technique

1986 ◽  
Author(s):  
J. LAMAR ◽  
R. BRUCE ◽  
J. PRIDE, JR. ◽  
R. SMITH ◽  
P. BROWN
Keyword(s):  
Flow Visualization ◽  
Leading Edge ◽  
Leading Edge Vortex ◽  
Edge Vortex

scholarly journals Petiolate wings: effects on the leading-edge vortex in flapping flight

2017 ◽  
Vol 7 (1) ◽  
pp. 20160084 ◽  
Author(s):  
Nathan Phillips ◽  
Kevin Knowles ◽  
Richard J. Bomphrey
Keyword(s):  
Lift Coefficient ◽  
Leading Edge ◽  
Field Measurements ◽  
Wing Surface ◽  
Tip Vortex ◽  
Leading Edge Vortex ◽  
Crane Flies ◽  
Image Velocimetry ◽  
Edge Vortex ◽  
Wing Stroke

The wings of many insect species including crane flies and damselflies are petiolate (on stalks), with the wing planform beginning some distance away from the wing hinge, rather than at the hinge. The aerodynamic impact of flapping petiolate wings is relatively unknown, particularly on the formation of the lift-augmenting leading-edge vortex (LEV): a key flow structure exploited by many insects, birds and bats to enhance their lift coefficient. We investigated the aerodynamic implications of petiolation P using particle image velocimetry flow field measurements on an array of rectangular wings of aspect ratio 3 and petiolation values of P = 1–3. The wings were driven using a mechanical device, the ‘Flapperatus’, to produce highly repeatable insect-like kinematics. The wings maintained a constant Reynolds number of 1400 and dimensionless stroke amplitude Λ * (number of chords traversed by the wingtip) of 6.5 across all test cases. Our results showed that for more petiolate wings the LEV is generally larger, stronger in circulation, and covers a greater area of the wing surface, particularly at the mid-span and inboard locations early in the wing stroke cycle. In each case, the LEV was initially arch-like in form with its outboard end terminating in a focus-sink on the wing surface, before transitioning to become continuous with the tip vortex thereafter. In the second half of the wing stroke, more petiolate wings exhibit a more detached LEV, with detachment initiating at approximately 70% and 50% span for P = 1 and 3, respectively. As a consequence, lift coefficients based on the LEV are higher in the first half of the wing stroke for petiolate wings, but more comparable in the second half. Time-averaged LEV lift coefficients show a general rise with petiolation over the range tested.

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