Low Reynolds Number Acceleration of Flat Plate Wings at High Incidence (Invited)

Stevens, Prrj; Babinsky, Holger; Manar, Field; Mancini, Peter; Jones, Anya R.; Granlund, KO; Ol, MV; Nakata, T.; Phillips, Nathan; Bomphrey, Richard J.; Gozukara, A

doi:10.2514/6.2016-0286

Cited by 16 publications

(14 citation statements)

References 5 publications

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“…Recently, it has been shown that between rotation and translation cases, the progression of the LEV over the wing surface is initially very similar before the LEV detaches for the translating wing, but remains attached if the wing is rotating [36]. A large collaborative effort across many research groups compared cases of revolving and translating rectangular wings at both fixed and time-varying angles of attack [37,38]. They found consistent LEV shedding for the translating wings [37] and that, whether wings were revolving or translating, there was no significant effect on the mean force coefficients after the initial vortex growth [38].…”

Section: Introductionmentioning

confidence: 99%

“…A large collaborative effort across many research groups compared cases of revolving and translating rectangular wings at both fixed and time-varying angles of attack [37,38]. They found consistent LEV shedding for the translating wings [37] and that, whether wings were revolving or translating, there was no significant effect on the mean force coefficients after the initial vortex growth [38]. This suggests that whether the LEV is attached to a revolving wing, or detaching from a translating wing the lift generated does not differ substantially.…”

Section: Introductionmentioning

confidence: 99%

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

2017

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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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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

2017

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“…Vortex breakup was seen for the accelerating (surging) flat plate cases. 9 Leading-edge and trailing-edge vortices were shown to convect downstream at differing speeds. 9 One study by Bernal 10 showed that the leading-edge vortex and trailing-edge vortex merged downstream and a new leading-edge vortex was formed.…”

Section: B Flat Plate Simulations and Dynamic Stallmentioning

confidence: 99%

“…9 Leading-edge and trailing-edge vortices were shown to convect downstream at differing speeds. 9 One study by Bernal 10 showed that the leading-edge vortex and trailing-edge vortex merged downstream and a new leading-edge vortex was formed. Some arching of the leading-edge vortex was observed for pitching motion by Jones et al 11…”

Section: B Flat Plate Simulations and Dynamic Stallmentioning

confidence: 99%

Toward Simulating a Pitch-Up Maneuver for a Small Unmanned Aerial Vehicle

Blake

Thompson

2016

46th AIAA Fluid Dynamics Conference

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The heaving of a flat plate was investigated in order to determine computational requirements for simulating a pitch-up maneuver for a Small Unmanned Aerial Vehicle (SUAS). A second-order, unstructured finite volume code was employed in conjunction with a Hybrid RANS/LES turbulence model to study the flowfield structures. Results predicted using the second-order method compared favorably to simulations by Visbal that employed a higher-order, structured-grid LES method. Large-scale flow structures and phase-averaged aerodynamic forces were accurately predicted. Greater spatial and temporal resolution is needed to resolve smaller scale structures. The results shown here demonstrate that the combined use of a second-order, unstructured method and a Hybrid RANS/LES turbulence model is an appropriate strategy for simulating an SUAS vehicle undergoing a high angle-of-attack maneuver.

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“…= geometric aspect ratio (=2), b 2 /S, m AR eff = effective aspect ratio, 2* AR , m b = wing wetted span, 2*c, m C D = drag coefficient, 2*D/U 2 = angle of attack, degree α" m = maximum pitch acceleration, degrees per second squared α(t) = pitch rate, degrees per second U ∞ = constant free stream velocity, meter per second…”

Section: Armentioning

confidence: 99%

Direct Force Measurements During Transient Flow about Pitching Flat Plates

Yu¹,

Bernal

2017

55th AIAA Aerospace Sciences Meeting

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This paper presents transient flow phenomena in terms of angles of attack by means of direct force measurement on pitching flat plate wings at a constant pitch acceleration. The wing motion is different from the most commonly used wing motion at constant pitch rates but generates comparable aerodynamics in a relatively short time. The wings were pitched from zero to maximum angles of attack ranging from 3 degrees to 42 degrees at mid-chord in a constant free stream Reynolds number of 8,900. Three wing planform shapes with the same effective aspect ratio four are considered: rectangle, trapezoid, and triangle. Results show that the unsteady forces are developed following the similar trend as the maximum angle of attack is increased, giving a positive normal force and negative axial force extreme. The transient flow, occurring at the maximum angles of attack before steady state, gives oscillatory characteristics on both normal force and axial force coefficients, and further yields oscillatory lift and drag coefficients. The multiple extremes of positive normal force and negative axial force are in phase. These oscillation phenomena are more vigorous for rectangular and trapezoidal wings, especially at the angle of attack higher than 24 degrees, than for triangular wing. Two types of vortex dynamic system are further revealed from Strouhal number analysis.

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Low Reynolds Number Acceleration of Flat Plate Wings at High Incidence (Invited)

Cited by 16 publications

References 5 publications

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

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

Toward Simulating a Pitch-Up Maneuver for a Small Unmanned Aerial Vehicle

Direct Force Measurements During Transient Flow about Pitching Flat Plates

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