Characterisation of Buffet on a Civil Aircraft Wing

Lawson, Sally N.; Greenwell, D. I.; Quinn, Mark K.

doi:10.2514/6.2016-1309

Cited by 36 publications

(43 citation statements)

References 6 publications

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“…The flow conditions reported in this paper have been corrected for wind tunnel interference effects and are compatible with previous publications (Lawson et al 2016;Masini et al 2017). Specifically, in half-model testing where the model is mounted to the floor, interference effects arise from the floor and sidewalls.…”

Section: Wind Tunnel Testing and Model Descriptionsupporting

confidence: 84%

“…Experimentally, the structural response can be directly measured from strain gauges and accelerometers. Lawson et al (2016) scrutinised several of these criteria using static and dynamic data for the RBC12 half-model. Good agreement between the strain gauge and accelerometer divergence, which mainly respond to wing bending, and aerodynamic indicators based on trailing-edge pressure divergence at 80 % semi-span and lift-curve slope reduction was reported.…”

Section: Experimental Buffet Onset Indicationmentioning

confidence: 99%

“…Early applications in transonic wind tunnels (Steimle, Karhoff & Schröder 2012;Merienne et al 2013) had poor resolution and restricted coverage, limited by the paint composition, its application, and camera technology. Having demonstrated the potential to clarify the flow mechanisms of complex flows, this rapidly evolving technique attracted attention, with recent experiments successfully acquiring unsteady pressure over the entire wing surface (Lawson, Greenwell & Quinn 2016;Sugioka et al 2018). In effect, rather than being confined to the discrete locations of pressure transducers, analysis is enabled over a much wider area, giving critical insight as discussed herein.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of a civil aircraft wing transonic shock buffet experiment

2019

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The physical mechanism governing the onset of transonic shock buffet on swept wings remains elusive, with no unequivocal description forthcoming despite over half a century of research. This paper elucidates the fundamental flow physics on a civil aircraft wing using an extensive experimental database from a transonic wind tunnel facility. The analysis covers a wide range of flow conditions at a Reynolds number of around 3.6 × 10 6 . Data at pre-buffet conditions and beyond onset are assessed for Mach numbers between 0.70 and 0.84. Critically, unsteady surface pressure data of high spatial and temporal resolution acquired by dynamic pressure-sensitive paint is analysed, in addition to conventional data from pressure transducers and a root strain gauge. We identify two distinct phenomena in shock buffet conditions. First, we highlight a low-frequency shock unsteadiness for Strouhal numbers between 0.05 and 0.15, based on mean aerodynamic chord and reference free stream velocity. This has a characteristic wavelength of approximately 0.8 semi-span lengths (equivalent to three mean aerodynamic chords). Such shock unsteadiness is already observed at low-incidence conditions, below the buffet onset defined by traditional indicators. This has the effect of propagating disturbances predominantly in the inboard direction, depending on localised separation, with a dimensionless convection speed of approximately 0.26 for a Strouhal number of 0.09. Second, we describe a broadband higher-frequency behaviour for Strouhal numbers between 0.2 and 0.5 with a wavelength of 0.2 to 0.3 semi-span lengths (0.6 to 1.2 mean aerodynamic chords). This outboard propagation is confined to the tip region, similar to previously reported buffet cells believed to constitute the shock buffet instability on conventional swept wings. Interestingly, a dimensionless outboard convection speed of approximately 0.26, coinciding with the low-frequency shock unsteadiness, is found to be nearly independent of frequency. We characterise these coexisting phenomena by use of signal processing tools and modal analysis of the dynamic pressure-sensitive paint data, specifically proper orthogonal and dynamic mode decomposition. The results are scrutinised within the context of a broader research effort, including numerical simulation, and viewed alongside other experiments. We anticipate our findings will help to clarify experimental and numerical observations in edge-of-the-envelope conditions and to ultimately inform buffet-control strategies.

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Section: Wind Tunnel Testing and Model Descriptionsupporting

confidence: 84%

Section: Experimental Buffet Onset Indicationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Analysis of a civil aircraft wing transonic shock buffet experiment

2019

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“…Whereas aerofoil buffet in turbulent flow is characterised by large chord-wise shock excursions at dominant Strouhal numbers of 0.06 to 0.07, wing buffet typically comes with lower amplitude shock motions and is more broadband with up to an order of magnitude higher frequencies (Dandois 2016). A span-wise outboard propagation of 'buffet cells' (a term coined by Iovnovich & Raveh (2015)), which is believed to constitute the instability, has been reported both in experimental and numerical studies (Lawson et al 2016;Koike et al 2016;Sartor & Timme 2017). A span-wise inboard propagation has also been identified experimentally at lower frequencies (Dandois 2016;Masini et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Global instability of wing shock-buffet onset

Timme

2020

J. Fluid Mech.

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Shock buffet on wings encountered in edge-of-the-envelope transonic flight remains an unresolved and disputed flow phenomenon, challenging both fundamental fluid mechanics and applied aircraft aerodynamics. The question of global instability leading to flow unsteadiness is addressed herein. It is shown for the first time that incipient threedimensional shock buffet is governed by the dynamics of a single unstable linear eigenmode with its spatial structure describing previously reported buffet cells. An inner-outer Krylov approach is proposed to solve the arising large-scale eigenvalue problem iteratively using shift-and-invert spectral transformation and sparse iterative linear solver. The established numerical strategy with an industrial flow solver means that a practical noncanonical test case at high-Re flow condition can be investigated. A modern wing design with publicly available geometry and experimental data for code validation is studied. The numerical findings can be exploited for routes to flow control and model reduction. †

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“…The ability to take field measurements of pressure has given researchers and aircraft designers new levels of insight into the flow physics they are investigating [1]. One area of interest is investigations of unsteady flows [2,3] where not only steady components of pressure but oscillating components and even aerodynamic modal shapes have been measured effectively. However, traditional (steady-state) PSP systems can often be large installations comprising of up to a dozen cameras with a similar number of lamps.…”

Section: Introductionmentioning

confidence: 99%

Miniaturisation of Pressure-Sensitive Paint Measurement Systems Using Low-Cost, Miniaturised Machine Vision Cameras

Quinn

Spinosa

Roberts

2017

Sensors

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Measurements of pressure-sensitive paint (PSP) have been performed using new or non-scientific imaging technology based on machine vision tools. Machine vision camera systems are typically used for automated inspection or process monitoring. Such devices offer the benefits of lower cost and reduced size compared with typically scientific-grade cameras; however, their optical qualities and suitability have yet to be determined. This research intends to show relevant imaging characteristics and also show the applicability of such imaging technology for PSP. Details of camera performance are benchmarked and compared to standard scientific imaging equipment and subsequent PSP tests are conducted using a static calibration chamber. The findings demonstrate that machine vision technology can be used for PSP measurements, opening up the possibility of performing measurements on-board small-scale model such as those used for wind tunnel testing or measurements in confined spaces with limited optical access.

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Characterisation of Buffet on a Civil Aircraft Wing

Cited by 36 publications

References 6 publications

Analysis of a civil aircraft wing transonic shock buffet experiment

Analysis of a civil aircraft wing transonic shock buffet experiment

Global instability of wing shock-buffet onset

Miniaturisation of Pressure-Sensitive Paint Measurement Systems Using Low-Cost, Miniaturised Machine Vision Cameras

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