Wind tunnel experiments on airframe noise sources of transport aircraft

Grosche, F.-R.; Schneider, G.; Stiewitt, H.

doi:10.2514/6.1997-1642

Cited by 10 publications

(4 citation statements)

References 7 publications

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“…At least some of these model problems are amenable to analytic solution and allow a comparison with our computational results. The present investigation is intended to prepare the ground for the computation of resonaces in high lift devices where slat noise, together with the noise from flaps and landing gears, is one of the major sources of airframe noise (Grosche, Schneider & Stiewitt 1997;Khorrami, Berkman & Choudhari 2000;Dobrzynski, Gehlhar & Buchholz 2001;or Olson 2003 and the literature cited therein).…”

Section: Introductionmentioning

confidence: 99%

On resonances in open systems

Hein¹,

Hohage

Koch³

2004

J. Fluid Mech.

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An open system or open resonator is a domain of wave activity separated from the exterior by a partly open or partly transparent surface. Such open resonators lose energy to infinity through radiation. The numerical computation of the corresponding resonances is complicated by spurious reflections of the outgoing waves at the necessarily finite grid boundaries. These reflections can be reduced to extremely low levels by applying perfectly matched layer (PML) absorbing boundary conditions, which separate the discrete resonances from the continuous spectrum. Using a simple one-dimensional model problem, the influence of the various PML parameters is determined by a numerical error analysis. In addition to one-dimensional open resonators, two-dimensional open resonators as well as various resonating structures in waveguides are considered, and the resonant spectra and selected modes are evaluated. For the first time, leaky modes are computed for several resonating structures in a waveguide in addition to the trapped modes published in the literature. In applications, leaky mode resonances are often more important than trapped mode resonances. Gap tones, observed in a model problem of high-lift configurations, are identified as transversal resonant modes with the lowest radiation losses.

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Section: Introductionmentioning

confidence: 99%

On resonances in open systems

Hein¹,

Hohage

Koch³

2004

J. Fluid Mech.

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“…However, determining source distributions about models requires mechanical movement of these sometimes very large systems. These systems are still found to be useful even today, especially in some larger test facilities 6,7 . Also in the 1970's, measurements involving directional (or phased) arrays of microphones were examined 8,9 using time delay and sum techniques.…”

Section: Introductionmentioning

confidence: 99%

Effect of directional array size on the measurement of airframe noise components

Thomas

Humphreys

1999

5th AIAA/CEAS Aeroacoustics Conference and Exhibit

131

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A study was conducted to examine the effects of overall size of directional (or phased) arrays on the measurement of aeroacoustic components. An airframe model was mounted in the potential core of an open-jet windtunnel, with the directional arrays located outside the flow in an anechoic environment. Two array systems were used; one with a solid measurement angle that encompasses 31.6° of source directivity and a smaller one that encompasses 7.2°. The arrays, and sub-arrays of various sizes, measured noise from a calibrator source and flap edge model setups. In these cases, noise was emitted from relatively small, but finite size source regions, with intense levels compared to other sources. Although the larger arrays revealed much more source region detail, the measured source levels were substantially reduced due to finer resolution compared to that of the smaller arrays. To better understand the measurements quantitatively, an analytical model was used to define the basic relationships between array to source region sizes and measured output level. Also, the effect of noise scattering by shear layer turbulence was examined using the present data and those of previous studies. Taken together, the two effects were sufficient to explain spectral level differences between arrays of different sizes. An important result of this study is that total (integrated) noise source levels are retrievable and the levels are independent of the array size as long as certain experimental and processing criteria are met. The criteria for both open and closed tunnels are discussed. The success of special

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“…Recents experiments have also indicated that, while the noise from high-lift devices is likely to dominate for mid-size aircraft, landing gear noise will become more significant for large aircraft 3,4 . The landing gear flow field can also potentially affect the flaps located downstream.…”

Section: Introductionmentioning

confidence: 96%

CFD investigation of noise around a landing gear

Fortin

Syms

Clark

et al. 2012

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

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A scaled landing gear has recently been tested in the NRC 0.9 m 3/4-open jet wind tunnel. It provided experimental data that were used to investigate the capability and methodology of a CFD flow solver to predict adequately the noise generated on the landing gear surfaces and in its wake. Near-field and far-field noise predictions using CFD were carried out. FFTs of the landing gear surfaces for a given frequency were also carried out. Comparison of the results demonstrates that CFD can predict adequately the noise around complex geometries such as landing gears. Nomenclature C p = pressure coefficient dB = decibels f = frequency FFT = fast Fourier transform Hz = hertz k = turbulent kinetic energy SPL = sound pressure level u ' = local perturbation velocity X,Y,Z = axis coordinates in wind tunnel y + = law-of-the-wall coordinate ∆ = cell dimension ε = turbulent dissipation rate

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Wind tunnel experiments on airframe noise sources of transport aircraft

Cited by 10 publications

References 7 publications

On resonances in open systems

On resonances in open systems

Effect of directional array size on the measurement of airframe noise components

CFD investigation of noise around a landing gear

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