Aeroacoustic Wind Tunnel Measurements on a 2D High-Lift Configuration

Kolb, Alexander; Faulhaber, Peter; Drobietz, Roger; Grünewald, Michael

doi:10.2514/6.2007-3447

Cited by 62 publications

(43 citation statements)

References 21 publications

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“…This has been observed by Roger & Perennes (2000) and Kolb et al (2007) among others who argued that the tonal components occurring in the low-frequency range are similar to the Rossiter modes of cavity flows.…”

Section: Pressure Fluctuationsmentioning

confidence: 58%

Numerical investigation of the flow dynamics past a three-element aerofoil

2013

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A numerical investigation of the flow dynamics around a two-dimensional high-lift configuration was carried out by means of a zonal detached eddy simulation (ZDES) technique for flow conditions corresponding to aircraft approach. Both slat and flap regions have been scrutinized and compared with experimental data available in the literature. It is shown that slat and flap coves behave like shallow cavities. The distance between the upstream cusp and the downstream edge is the relevant length scale for each cove taken separately. Consistently with previous findings, this study indicates that the maximum of the broadband spectrum of slat (respectively flap) pressure fluctuations occurs for Strouhal numbers 0.5 St 4 when based on slat chord (respectively on flap chord) and free-stream velocity. It is shown that mode (n) of the slat cove and mode (n + 1) of the flap cove are very close making a coherent phase relationship possible. A large-scale coupled self-sustained oscillations mechanism between slat and flap cavities, evidenced by spectral analysis, occurs at a Strouhal number St = 3-6 based on the main wing chord and free-stream velocity. This yields to an acoustic feedback mechanism characterized by a normalized frequency depending on the free stream Mach number like St = (1 − M 2 0 )/2M 0 . The present result appears to line up with the findings by Hein et al. (J. Fluid Mech., vol. 582, 2007, pp. 179-202) who showed that two types of resonance could exist: surface waves ones, scaling with the total aerofoil length and longitudinal cavity-type resonances, scaling with the slat cove length.

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Section: Pressure Fluctuationsmentioning

confidence: 58%

Numerical investigation of the flow dynamics past a three-element aerofoil

2013

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“…Fig.8 shows spectral density and 1/3-octave noise spectra with and without slat [10]. Significant increase in noise for the wing configuration with deployed slat, as well as the narrow-band peaks in the spectrum, are clearly seen.…”

Section: A Reference Slatmentioning

confidence: 84%

Effect of sweep on chevron slat noise

Kopiev¹,

Zaitsev²,

Belyaev³

2013

19th AIAA/CEAS Aeroacoustics Conference

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Experimental investigation of the effect of sweep on slat noise has been performed for small-scale (1:18) models, which indicates that sweep can significantly modify airframe noise spectra. The new method of airframe noise mitigation based on the concept of chevron geometry for the slat's lower egde, which has been previously proved efficient for 2D wing models, has been assessed for the swept wing. It has been demonstrated that the method is effective for narrowband peak mitigation both for swept wing and 2D wing.

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“…As indicated by these authors, the use of such a device makes it possible to suppress the main shear layer and its associated feedback loop, which appears as a convincing indication that the tonal peaks are strongly linked to the presence of the main shear layer. In their study, Kolb et al 7 applied quite successfully Rossiter's semi-empirical formula to recover analytically the discrete frequencies observed in their experiments. However, applying directly Rossiter's formula -originally developed for rectangular cavities 8 -to the flow inside the slat cove seems questionable.…”

Section: E Physical Interpretation For Tonal Peaksmentioning

confidence: 97%

Slat noise measurement and numerical prediction in the VALIANT programme

Manoha¹,

Terracol²,

Lemoine

et al. 2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

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In the context of the on-going EC research program VALIANT, mechanisms of slat noise generation are studied on the basis of a simple but representative 2-element (slat and main body) airfoil, for which a detailed experimental aerodynamic/acoustic database has been collected in the open jet facility at Ecole Centrale de Lyon (ECL) at a Reynolds number, based on the airfoil chord, of about one million. Then several CFD/CAA prediction methods have been compared, improved and validated against this database.The airfoil shape has been optimized by Onera with the objectives of isolating the slat noise sources from other spurious sources, while minimizing the airfoil total lift and the wind tunnel mean flow deflection. The tests at ECL provided aerodynamic data (static and unsteady wall pressure data, hot-wire probe measurements) and farfield noise acquisitions, including directivity characterization and noise sources localization using Onera's microphone antenna. Then an unsteady zonal hybrid RANS/LES simulation has been performed using Onera's FUNk solver, providing a comprehensive description and physical analysis of the unsteady flow inside the slat cove. The computed and measured wall pressure spectra are in fair qualitative and quantitative agreement, both being characterized by several tonal peaks emerging from a global broadband content. The noise maps confirmed that these peaks are actually generated by the slat cove region. These tones are attributed to a cavity feedback loop mechanism involving the impact of the main shear layer on the slat pressure side, and a theoretical law predicting the tone frequencies has been proposed. Finally, a farfield noise prediction is achieved, using a Ffowcs Williams-Hawking integration (Onera's MIA solver), from CFD unsteady data stored on a porous surface located at the external boundaries of the CFD domain. Corrections are proposed to account for (i) the difference between experimental and computational airfoil spans, based on un-correlated spanwise duplication of the CFD domain, (ii) the acoustic installation effects, studied via BEM computations using Onera's Bemuse solver, due to the test set-up side plates and the airfoil surfaces which were not included in the CFD domain. With these corrections, measured and predicted farfield noise spectra and overall sound pressure levels are in fair agreement. I ContextIn the on-going EC research program VALIANT (VALidation and Improvement of Airframe Noise prediction Tools) coordinated by the Von Karman Institute (Brussels, Belgium) basic mechanisms of airframe noise (AFN) are studied through a dual approach, • to generate a detailed, accurate experimental database on broadband noise associated with simple but representative configurations, including the turbulent flow sources causing the noise and, • to validate and improve CFD/CAA tools for prediction of the corresponding type of broadband AFN and generate a detailed numerical database. The following specific flow configurations revealing the basic mechanisms of AFN generated by ...

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Aeroacoustic Wind Tunnel Measurements on a 2D High-Lift Configuration

Cited by 62 publications

References 21 publications

Numerical investigation of the flow dynamics past a three-element aerofoil

Numerical investigation of the flow dynamics past a three-element aerofoil

Effect of sweep on chevron slat noise

Slat noise measurement and numerical prediction in the VALIANT programme

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