A Conceptual Study of Leading-Edge-Vortex Enhancement by Blowing

Bradley, R. G.; Wray, W.O.

doi:10.2514/3.60318

Cited by 48 publications

(8 citation statements)

References 2 publications

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“…The discovery of the leading-edge vortex (LEV) in a flying insect closely links biology to engineering because the potential of trapped or wing attached vortices for lift enhancement has long been recognised in aerodynamics (Bradley et al 1974;Campbell 1976;Dixon et al 1973;Gleason and Roskam 1972;Krall and Haight 1972;Kruppa 1977;Maxworthy 1979;Rossow 1978;Sunada et al 1993). A comprehensive review on the physics of vortex lift is given by Wu et al (1991).…”

Section: General Introductionmentioning

confidence: 99%

The mechanisms of lift enhancement in insect flight

Lehmann

2004

Naturwissenschaften

157

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Recent studies have revealed a diverse array of fluid dynamic phenomena that enhance lift production during flapping insect flight. Physical and analytical models of oscillating wings have demonstrated that a prominent vortex attached to the wing's leading edge augments lift production throughout the translational parts of the stroke cycle, whereas aerodynamic circulation due to wing rotation, and possibly momentum transfer due to a recovery of wake energy, may increase lift at the end of each half stroke. Compared to the predictions derived from conventional steady-state aerodynamic theory, these unsteady aerodynamic mechanisms may account for the majority of total lift produced by a flying insect. In addition to contributing to the lift required to keep the insect aloft, manipulation of the translational and rotational aerodynamic mechanisms may provide a potent means by which a flying animal can modulate direction and magnitude of flight forces for manoeuvring flight control and steering behaviour. The attainment of flight, including the ability to control aerodynamic forces by the neuromuscular system, is a classic paradigm of the remarkable adaptability that flying insects have for utilising the principles of unsteady fluid dynamics. Applying these principles to biology broadens our understanding of how the diverse patterns of wing motion displayed by the different insect species have been developed throughout their long evolutionary history.

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Section: General Introductionmentioning

confidence: 99%

The mechanisms of lift enhancement in insect flight

Lehmann

2004

Naturwissenschaften

157

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“…Dixon [35] believed that SWB on the wing provides sweeplike effects as the SWB jets are entrained in the leading-edge vortices. Bradley and Wray [38] credited the success of their blowing technique to the increase in the vortex stability, which to some extent is related to the longitudinal flow in the vortex core. Passive vortex breakdown control devices such as strakes, LEXs, or double-delta wings [14][15][16][17][18][19][20][21][22] are used in numerous aircrafts.…”

Section: Nomenclaturementioning

confidence: 98%

“…These include mechanical devices such as leading-edge flaps [9][10][11][12], apex fences [13], canards, strakes, leading-edge extensions (LEXs), or double-delta wing [14][15][16][17][18][19][20][21][22] and pneumatic techniques such as trailing-edge blowing [23][24][25][26][27][28] or suction [29], along-the-core blowing technique [30][31][32][33][34], spanwise blowing (SWB) [35][36][37], and some other blowing/suction techniques [38] with different blowing/suction locations and orientations.…”

Section: Nomenclaturementioning

confidence: 99%

Forebody Slot Blowing on Vortex Breakdown and Load Over a Delta Wing

2008

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shows that a forebody slot blowing technique significantly delays vortex breakdown over a delta wing. Blowing only on one side while delaying vortex breakdown has an opposite effect on the nonblowing side. Although the authors provided a plausible explanation for the observed behavior, no concrete evidence was given. In this paper, we address this issue and further evaluate the effects of symmetric and differential blowing on the aerodynamic loads. Flow visualization and force measurement were carried out in a water tunnel at a Reynolds number of 8:5 10 4 . Our study shows that the differing effect of differential blowing can be traced to a combination of forebody slot blowing itself and the interaction of the vortices from both sides resulting in a side-slip-like effect. Moreover, symmetrical forebody slot blowing, apart from producing a significant delay in the formation of vortex breakdown, increases the lift by more than 5%. Differential blowing can be used to manipulate the vortex breakdown position and change the roll moment of the wing, which suggests that the method can be a potential means for roll control. Nomenclature= blowing momentum coefficient for port side slot C S = blowing momentum coefficient for starboard side slot c = root chord Q = volume flow rate of blowing q = dynamic pressure of freestream Re = Reynolds number, Uc=v S = area of delta wing U = freestream velocity V j = average slot exit velocity X b = vortex breakdown position from the apex of the wing X bmean = mean vortex breakdown position X bmean P = mean port side vortex breakdown position X bmean S = mean starboard side vortex breakdown position = kinematic viscosity of water = density of blowing fluid

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“…Flow visualization pictures taken by Bradley and Wray (1974) of the vortex exhibited a more coherent core and delay in breakdown which is due to the increase in axial convection. When compared with Polhamus' theory, full vortex lift was achieved beyond the normal angle of attack for maximum lift (Fig.…”

Section: Blowingmentioning

confidence: 99%

“…Bradley and Wray (1974) and Campbell (1976) achieved higher lift, a delay in stall and better drag polar as a result of the spanwise blowing along the leading edge.…”

Section: Blowingmentioning

confidence: 99%