Aircraft wake dissipation by sinusoidal instability and vortex breakdown

Bilanin, Alan J.

doi:10.2514/6.1973-107

Cited by 37 publications

(19 citation statements)

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“…Naughton et al [59] examined compressibility effects on the swirl induced growth of a jet, and found no significant influence, supporting the validity of the low-mach number assumption. Theoretical studies on VB were attempted to find simple descriptions of the causes and mechanisms based on inviscid model vortices [48] or wave theory [8,9,47,70,81]; and hydrodynamic instability theory on VB [50,52,53] was developed to find criteria for instability.…”

Section: Studies Of Vortex Breakdownmentioning

confidence: 99%

Large Eddy Simulations of Swirling Non-premixed Flames With Flamelet Models: A Comparison of Numerical Methods

Kempf

Malalasekera

Ranga-Dinesh

et al. 2008

Flow Turbulence Combust

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This work investigates the application of large eddy simulation (LES) to selected cases of the turbulent non-premixed Sydney swirl flames. Two research groups (Loughborough University, LU and Imperial College, IC) have simulated these cases for different parameter sets, using two different and independent LES methods. The simulations of the non-reactive turbulent flow predicted the experimental results with good agreement and both simulations captured the recirculation structures and the vortex breakdown without major difficulties. For the reactive cases, the LES predictions were less satisfactory, and using two independent simulations has helped to understand the shortcomings of each. Furthermore one of the flames (SMH2) was found to be exceptionally hard to predict, which was supported by the lower amount of turbulent kinetic energy that was resolved in this case. However, the LES has identified modes of flame instability that were similar to those observed in some of the experiments.

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Section: Studies Of Vortex Breakdownmentioning

confidence: 99%

Large Eddy Simulations of Swirling Non-premixed Flames With Flamelet Models: A Comparison of Numerical Methods

Kempf

Malalasekera

Ranga-Dinesh

et al. 2008

Flow Turbulence Combust

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“…These disturbances would be wrapped up into the vortex and create variations along its axis. This has been done experimentally 32 and during flight 33 to excite the Crow instability between trailing vortices. The current simulations, however, are applicable to instabilities that occur between a trailing vortex and the secondary vortex that is created as the trailing vortex interacts with the ground.…”

Section: B Initial and Boundary Conditionsmentioning

confidence: 99%

The three-dimensional interaction of a vortex pair with a wall

Luton

Ragab

1997

Physics of Fluids

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Articles you may be interested inThe onset of three-dimensional centrifugal global modes and their nonlinear development in a recirculating flow over a flat surface Phys. Fluids 22, 114102 (2010) The interaction of vortices passing near a solid surface has been examined using direct numerical simulation. The configuration studied is a counter-rotating vortex pair approaching a wall in an otherwise quiescent fluid. The focus of these simulations is on the three-dimensional effects, of which little is known. To the authors' knowledge, this is the first three-dimensional simulation that lends support to the short-wavelength instability of the secondary vortex. It has been shown how this Crow-type instability leads to three dimensionality after the rebound of a vortex pair. The growth of the instability of the secondary vortex in the presence of the stronger primary vortex leads to the turning and intense stretching of the secondary vortex. As the instability grows the secondary vortex is bent, stretched, and wrapped around the stronger primary. During this process reconnection was observed between the two secondary vortices. Reconnection also begins between the primary and secondary vortices but the weaker secondary vortex dissipates before the primary, leaving reconnection incomplete. Evidence is presented for a new type of energy cascade based on the short-wavelength instability and the formation of continual smaller vortices at the wall. Ultimately the secondary vortex is destroyed by stretching and dissipation leaving the primary vortex with a permanently distorted shape but relatively unaffected strength compared to an isolated vortex.

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“…The latter method actively forces the breakup of vortices, for example, by pitching the vehicle (Chevalier, 1973) or differentially and time-dependently deflecting inboard and outboard control surfaces ("sloshing" of the lift distribution; Crow,1971, Crow and Bate, 1976; Haverkamp et al, 2005). This method was tested in a towing tank (Bilanin and Widnall, 1973), where measured amplification rates agreed qualitatively with theoretical predictions. Recently, a similar approach was pursued with a view to exploiting the multiple vortex growth mechanisms created by an airplane on approach with flaps-down (Crouch el al, 2001).…”

Section: Introductionmentioning

confidence: 99%

Active Management of Flap-Edge Trailing Vortices

Greenblatt

Yao

Vey

et al. 2008

4th Flow Control Conference

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The vortex hazard produced by large airliners and increasingly larger airliners entering service, combined with projected rapid increases in the demand for air transportation, is expected to act as a major impediment to increased air traffic capacity. Significant reduction in the vortex hazard is possible, however, by employing active vortex alleviation techniques that reduce the wake severity by dynamically modifying its vortex characteristics, providing that the techniques do not degrade performance or compromise safety and ride quality. With this as background, a series of experiments were performed, initially at NASA Langley Research Center and subsequently at the Berlin University of Technology in collaboration with the German Aerospace Center. The investigations demonstrated the basic mechanism for managing trailing vortices using retrofitted devices that are decoupled from conventional control surfaces. The basic premise for managing vortices advanced here is rooted in the erstwhile forgotten hypothesis of Albert Betz, as extended and verified ingeniously by Coleman duPont Donaldson and his collaborators. Using these devices, vortices may be perturbed at arbitrarily long wavelengths down to wavelengths less than a typical airliner wingspan and the oscillatory loads on the wings, and hence the vehicle, are small. Significant flexibility in the specific device has been demonstrated using local passive and active separation control as well as local circulation control via Gurney flaps. The method is now in a position to be tested in a wind tunnel with a longer test section on a scaled airliner configuration. Alternatively, the method can be tested directly in a towing tank, on a model aircraft, a light aircraft or a full-scale airliner. The authors believed that this method will have significant appeal from an industry perspective due to its retrofit potential with little to no impact on cruise (devices tucked away in the cove or retracted); low operating power requirements; small lift oscillations when deployed in a time-dependent manner; and significant flexibility with respect to the specific devices selected. American Institute of Aeronautics and Astronautics= slot width h G = Gurney flap height relative to the chord l G = Gurney flap span relative to the flap span L f = flap length, from slot to trailing-edge q = free-stream dynamic pressure r = distance measured form the vortex center Re = Reynolds number based on chord-length U j = peak jet slot blowing velocity U = free-stream velocity U,V,W = mean velocities in directions x,y,z X = distance from perturbation to wing trailing-edge x,y,z = coordinates measured from model leading-edge and root (left-hand system) = angle of attack s = static stall angle = flap deflection angle = wavelength = phase shift in degrees = vortex sheet strength, d /dy = bound circulation = rolled-up wake vortex strength = sweep-back angle x = streamwise vorticity, W/ y-V/ z * = indicates control

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Aircraft wake dissipation by sinusoidal instability and vortex breakdown

Cited by 37 publications

References 0 publications

Large Eddy Simulations of Swirling Non-premixed Flames With Flamelet Models: A Comparison of Numerical Methods

Large Eddy Simulations of Swirling Non-premixed Flames With Flamelet Models: A Comparison of Numerical Methods

The three-dimensional interaction of a vortex pair with a wall

Active Management of Flap-Edge Trailing Vortices

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