Comparison of Rotating and Translating Wings: Force Production and Vortex Characteristics

Manar, Field; Mancini, Peter; Mayo, David B.; Jones, Anya R.

doi:10.2514/1.j054422

Cited by 31 publications

(22 citation statements)

References 36 publications

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“…In heaving and pitching motions, leading edge vortices are shed soon after formation (Manar et al. 2015; Mancini et al. 2015), causing a transient burst of high thrust.…”

Section: Discussionmentioning

confidence: 99%

How dorsal fin sharpness affects swimming speed and economy

2019

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Multi-fin systems, like fish or fish-inspired vehicles, are governed by unsteady three-dimensional interactions between their multiple fins. In particular, dorsal/anal fins have received much attention because they are just upstream of the main thrust-producing fin: the caudal (tail) fin. We used a tuna-inspired fish model with variable fin sharpness to study the interaction between elongated dorsal/anal fins and caudal fins. We found that the performance enhancement is stronger than previously thought (15 % increase in swimming speed and 50 % increase in swimming economy) and is governed by a three-dimensional dorsal-fin-induced cross-flow that lowers the angle of attack on the caudal fin and promotes spanwise flow. Both simulations and multi-layer particle image velocimetry reveal that the cross-flow stabilizes the leading edge vortex on the caudal fin, similar to how wing strakes prevent stall during fixed-wing aircraft manoeuvres. Unlike other fin–fin interactions, this mechanism is phase-insensitive and offers a simple, passive solution for flow control over oscillating propulsors. Our results therefore improve our understanding of multi-fin flow interactions and suggest new insights into dorsal/anal fin shape and placement in fish and fish-inspired vehicles.

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“…In heaving and pitching motions, leading edge vortices are shed soon after formation (Manar et al. 2015; Mancini et al. 2015), causing a transient burst of high thrust.…”

Section: Discussionmentioning

confidence: 99%

How dorsal fin sharpness affects swimming speed and economy

2019

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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].…”

Section: Introductionmentioning

confidence: 99%

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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“…(2015), here called UB2, UB3 and UB4, respectively, and with slower accelerations and varying root cutouts from Manar et al. (2016) (UMD-fast) and Percin & van Oudheusden (2015) (TUD). We also compare the model with the more gradual acceleration experiment of Manar et al.…”

Section: Model Validation and Discussionmentioning

confidence: 99%

A simple vortex-loop-based model for unsteady rotating wings

Chowdhury

Ringuette

2019

J. Fluid Mech.

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An analytical model is developed for the lift force produced by unsteady rotating wings; this configuration is a simple representation of a flapping wing. Modelling this is important for the aerodynamic and control-system design for bio-inspired drones. Such efforts have often been limited to being two-dimensional, semi-empirical, sometimes computationally expensive, or quasi-steady. The current model is unsteady and three-dimensional, yet simple to implement, requiring knowledge of only the wing kinematics and geometry. Rotating wings produce a vortex loop consisting of the root vortex, leading-edge vortex, tip vortex and trailing-edge vortex, which grows with time. This is modelled as a tilted planar loop, geometrically specified by the wing size, orientation and motion. By equating the angular impulse of the vortex loop to that of the fluid volume driven by the wing, the circulatory lift force is derived. Potential flow theory gives the fluid-inertial lift. Adding these two contributions yields the total lift formula. The model shows good agreement with a range of experimental and computational cases. Also, a steady-state lift model is developed that compares well with previous work for various angles of attack.

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Comparison of Rotating and Translating Wings: Force Production and Vortex Characteristics

Cited by 31 publications

References 36 publications

How dorsal fin sharpness affects swimming speed and economy

How dorsal fin sharpness affects swimming speed and economy

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

A simple vortex-loop-based model for unsteady rotating wings

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