Large-Eddy Simulation of Boundary Layer Transition on Swept Wings

Xiaoli, Huai; Joslin, Ronald D.; Piomelli, Ugo

doi:10.1007/978-94-011-1032-7_36

Cited by 3 publications

(3 citation statements)

References 4 publications

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“…The numerical scheme and SGS models were first validated by the simulation of the evolution of linear and nonlinear stationary crossflow disturbances on a swept wedge (Huai, Joslin & Piomelli 1994) and of boundary-layer transition on a flat plate (Huai 1996;Huai et al 1997). For the stationary crossflow evolution, the LES results were in excellent agreement with the DNS results of Joslin & Streett (1994); although this comparison allowed us to validate the numerical scheme, the SGS eddy viscosity was very small at all locations (the flow was only undergoing the initial stages of transition).…”

Section: Solution Methodologymentioning

confidence: 99%

Large-eddy simulation of boundary-layer transition on a swept wedge

1999

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The spatial evolution of the disturbances that lead to boundary-layer transition on a swept wedge is computed by large-eddy simulations (LES). Stationary and travelling crossflow-vortex disturbances are generated using steady and random-amplitude suction and blowing on the wedge. For a fixed initial amplitude of the stationary vortex and low-amplitude unsteady disturbances, the LES show the evolution of stationary-dominated crossflow disturbances similar to previous simulations and experiments: linear amplification is followed by vortex roll-over and doubly inflectional velocity profiles just prior to transition. A high-frequency secondary instability is associated with the double inflection points in the velocity profiles. The harmonic modes of the primary disturbance were found to be amplified, while no energy was found in any subharmonic mode. The physical phenomena were significantly different when the stationary and travelling vortices have comparable initial amplitudes: in this case, the vortex roll-over does not occur and transition is dominated by the travelling-wave component.

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Section: Solution Methodologymentioning

confidence: 99%

Large-eddy simulation of boundary-layer transition on a swept wedge

1999

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“…The LES study by Mary (3) demonstrates, in particular, a substantial sensitivity of the predicted flow above the suction side to the near-wall treatment within one and the same LES strategy. There is also a numerical study of the development and transition of a three-dimensional boundary layer on a swept wing with its curvature neglected and its span assumed to be infinite (4) . These flow conditions, although very complex, are considerably simpler than those around the present wing, with its highly curved leading edge and twisted geometry.…”

Section: The Computational Approachmentioning

confidence: 99%

Large-eddy simulation of separated flow over a swept wing with approximate near-wall modelling

Leschziner

2007

Aeronaut. j.

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Moderate to high sweep is a feature of most modern aircraft, especially of military planes. When the wing is thin, with high leading-edge curvature, even modest incidence can lead to separation, unless elaborate flow-control measures are taken. Depending on the sweep, different regimes of complex separation phenomena arise on the suction side. At low sweep, the flow can exhibit some characteristics akin to 'closed' (bubble) separation, observed in two-dimensional geometries. At high sweep, separation is of the 'open' (vortex) type, characterised by multiple vortical structures and separation and reattachment lines on the suction side. The boundary between the two regimes is not distinct, however. At the line of separation, the flow may or may not be turbulent. Contamination from the spanwise motion favours transition on attachment, but close to the wing root (or apex) transition may occur in the separated shear layer. In the case of vortex separation, the flow above the wing is highly swirling and the vortex contains a core that moves at high speed in the axial direction. The body forces associated with the swirl can make the vortex super-critical, strongly damp turbulence and hence reduce the spreading rate of the vortex. Secondary separation zones also arise on the wing, adding to the ABSRACT The paper investigates, by means of a simulation methodology, the flow separating from a 40 degrees backward-swept wing at 9 degrees incidence and Reynolds number of 210,000, based on the wing-root chord length. The Simulation corresponds to LDA, PIV and suction-side-topology measurements for the same geometry, conducted by other investigators specifically to provide validation data. The finest block-structured mesh contains 23·6 million nodes and is organised in 256 blocks to maximise mesh quality and facilitate parallel solution on multi-processor machines. The near-wall layer is resolved, to a thickness of about y + = 20, by means of parabolised URANS equations that include an algebraic eddyviscosity model and from which the wall-shear stress is extracted to provide an unsteady boundary condition for the simulation. The numerical solution is in good agreement with the experimental behaviour over the 50-70% inboard portion of the span, but the simulation fails to resolve some complex features close to the wing tip, due to a premature leading-edge vortex breakdown and loss in vortex coherence. The comparisons and their discussion provide useful insight into various physical characteristics of this complex separated wing flow.

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“…The numerical scheme and SGS models had previously been validated in two studies: the rst was the calculation of subharmonic instability in a at-plate boundary layer (Huai, 1996;Huai et al, 1997); the second, the calculation of transition in a swept wing in presence of stationary disturbances only (Huai et al, 1994).…”

Section: Code Validationmentioning

confidence: 99%

Large-eddy simulation of laminar-turbulent transition in a swept-wing boundary layer

Xiaoli

Joslin

Piomelli

1997

35th Aerospace Sciences Meeting and Exhibit

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The spatial development of laminar-turbulent transition in a 45 swept-wing boundary layer is investigated using the large-eddy simulation approach. Both stationary and traveling disturbances are initiated by steady and random forcings. The numerical simulations reproduce the surface shear streaks typical of the crossow instability observed in experiments. Downstream of the transition location the wall shear stress is found to turn towards the streak direction. The strength of the stationary vortices grows exponentially, initially independent of the unsteady forcing amplitude and saturates at dierent levels during the later development, depending on the magnitude of the traveling vortices. Streamwise velocity contours show the evolution from a wave-like structure to the \half-mushroom" structure for the lower-amplitude, traveling-wave case, leading to double inection points in the wallnormal velocity proles prior to transition; the nonlinear interactions involving the stationary vortices are also much stronger, as indicated by the amplication of higher harmonics of the primary mode. The frequency spectrum of the traveling waves show a high frequency secondary instability prior to transition that, however, is not prominent in the higheramplitude traveling-wave case.

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Large-Eddy Simulation of Boundary Layer Transition on Swept Wings

Cited by 3 publications

References 4 publications

Large-eddy simulation of boundary-layer transition on a swept wedge

Large-eddy simulation of boundary-layer transition on a swept wedge

Large-eddy simulation of separated flow over a swept wing with approximate near-wall modelling

Large-eddy simulation of laminar-turbulent transition in a swept-wing boundary layer

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