Trailing-edge jet control of leading-edge vortices of a delta wing

Shih, Chiang; Ding, Zhong

doi:10.2514/3.13252

Cited by 47 publications

(27 citation statements)

References 23 publications

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“…• the Kelvin-Helmholtz instability in the shear layer emanating from the leading-edge; it results in the formation of rotational structures; 11,12 • the vortex wandering, which is a random displacement of the vortex around its time-averaged axis; this phenomenon can be explained by the interaction of the vortex with the vortical structures embedded in the shear layer; 13,14 • the vortex breakdown, which is the consequence of a wave propagation phenomenon; 8-10 • the helical mode instability downstream from the vortex breakdown location; this phenomenon can be related to the observations of the spiral shape of the vortex breakdown; 15,16 • oscillations of the vortex breakdown location. 17,18 Even if these unsteady phenomena persist with an increase in the freestream Mach number, the behavior of the whole vortical flow is modified in the transonic regime.…”

Section: Introductionmentioning

confidence: 99%

Compressibility effects on the vortical flow over a 65° sweep delta wing

2010

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Dynamically stretching and retracting wingspan has been widely observed in the flight of birds and bats, and its effects on the aerodynamic performance particularly lift generation are intriguing. The rectangular flat-plate flapping wing with a sinusoidally stretching and retracting wingspan is proposed as a simple model for biologically inspired dynamic morphing wings. Numerical simulations of the low-Reynolds-number flows around the flapping morphing wing are conducted in a parametric space by using the immersed boundary method. It is found that the instantaneous and time-averaged lift coefficients of the wing can be significantly enhanced by dynamically changing wingspan in a flapping cycle. The lift enhancement is caused by both changing the lifting surface area and manipulating the flow structures responsible to the vortex lift generation. The physical mechanisms behind the lift enhancement are explored by examining the three-dimensional flow structures around the flapping wing. C 2014 AIP Publishing LLC. [http://dx.

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Section: Introductionmentioning

confidence: 99%

Compressibility effects on the vortical flow over a 65° sweep delta wing

2010

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“…The values of the momentum coefficient used in the experiments are realistic for thrust-vectoring applications and also have been used by previous investigators [8][9][10][11][12][13]. Experiments were conducted for both periodic and transient (ramp) variations of the jet momentum coefficient.…”

Section: A Experimental Setupmentioning

confidence: 99%

“…At a sufficiently high angle of attack, the vortices undergo a sudden expansion known as vortex breakdown [6,7], which has adverse aerodynamic effects on delta wing performance. Several investigations [8][9][10][11][12][13] demonstrated that thrust-vectoring jets at the trailing edge could delay vortex breakdown significantly, up to 50% of wing chord. Therefore, significant effects on the aerodynamic forces and moments on the wings are expected.…”

Section: Introductionmentioning

confidence: 99%

Effects of Unsteady Trailing-Edge Blowing on Delta Wing Aerodynamics

Jiang

Wang

Gursul

2010

Journal of Aircraft

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The effects of unsteady trailing-edge blowing on delta wing aerodynamics were investigated experimentally to understand the aerodynamics-propulsion interaction for dynamic thrust vectoring. Two models with sweep angles of 50 and 65 deg, representing nonslender and slender delta wings, respectively, were tested in a water tunnel. Flow visualization and velocity and force measurements were conducted at stall and poststall incidences. For the periodic blowing, it was found that the dynamic response of leading-edge vortex breakdown and wing normal force coefficient exhibit phase lags for both nonslender and slender delta wings. The estimated time constants are larger than those reported in the literature for unsteady wings undergoing pitching or plunging. In the case of transient blowing, the time delay for the decelerating jet is significantly larger than that for the accelerating jet. The variation of the circulation and the reattachment process near the wing surface were studied by means of velocity measurements. The range of the estimated time constants is similar at the stall and poststall incidences for both the slender and nonslender wings.= dimensionless frequency, fc=U 1 q = freestream dynamic pressure Re = Reynolds number S w = wing surface area s = local semispan T = period t = wing thickness or time U jet = jet velocity U 1 = freestream velocity u = velocity X bd = distance from wing apex to leading-edge vortex breakdown location y jet = spanwise location of jet = wing incidence = jet pitch angle = circulation X bd = peak-to-peak amplitude of the variation of the vortex breakdown location = leading-edge sweep angle = fluid kinematic viscosity = air density = time constant = phase lag ! = angular frequency ! x = streamwise vorticity

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“…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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Trailing-edge jet control of leading-edge vortices of a delta wing

Cited by 47 publications

References 23 publications

Compressibility effects on the vortical flow over a 65° sweep delta wing

Compressibility effects on the vortical flow over a 65° sweep delta wing

Effects of Unsteady Trailing-Edge Blowing on Delta Wing Aerodynamics

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

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