Research into Landing Gear Airframe Noise Reduction

Dobrzynski, W.; Chow, L.C.; Guion, Pierre; Shiells, Derek

doi:10.2514/6.2002-2409

Cited by 44 publications

(17 citation statements)

References 2 publications

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“…Indeed airframe noise may be dominated by landing gear noise during approach to landing. 1 The noise produced by landing gears is broadband in nature. 2 The typical noise generating mechanism of a landing gear is that of a compact dipole whose strength is proportional to the unsteady force exerted on the fluid by the component.…”

Section: Introductionmentioning

confidence: 99%

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Use of Blowing Flow Control to Reduce Bluff Body Interaction Noise

2012

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When an unsteady wake from an upstream body impinges on a downstream body, the resultant interaction noise can be significant. The use of distributed blowing through the surface of a cylinder to reduce this source of noise was investigated in a series of experiments. The two bluff bodies in tandem were a cylinder and an H-beam. Two configurations were tested, one with the cylinder upstream of the H-beam (OH configuration) and the other with the H-beam upstream of the cylinder (HO configuration). The default separation distance was / = 2. These two configurations modelled the interaction noise due to large perturbations in the wake generated by an upstream component inducing unsteady pressure fluctuations on a downstream component. Blowing was used to break down the large flow structures in the wake and to modify the shear layers. The mean velocities and velocity fluctuations were determined in the flowfield. The application of blowing to the OH configuration reduced the ′ ′ component of the stress term. This resulted in a peak reduction of 9.3 dB at a Strouhal number of 0.2. There was a broadband noise reduction of 3.2 dB averaged over the frequency range 0.05 < < 5. The effect of blowing on the HO configuration was to inhibit the strong crossflow fluctuations ( ′ ′ ) between the Hbeam and the cylinder by delaying the reattachment of the shear layers onto the surface of the cylinder. This resulted in a large noise reduction of 13.2 dB at a Strouhal number of 0.8. There was a broadband noise reduction of 4.3 dB averaged over the frequency range 0.05 < < 6.3. The effect of blowing produced additional high frequency noise. This additional noise was minimised with blowing applied through a sintered plate with a very small pore diameter. NomenclatureBlowing area, m 2 Pressure coefficient Blowing coefficient Pore diameter, ṁ Volume flow rate, m 3 /s Distance to microphone, m Reference area, m 2 Strouhal number based on cylinder diameter Component separation distance, m Lighthill stress tensor, N/m 2 Perforated plate thickness, m , , Non-dimensional cartesian components of velocity vector ′ ′ , ′ ′ , ′ ′ Non-dimensional components of Reynolds stress tensor ∞ Freestream velocity, m/s , , Cartesian coordinates, positive downstream, positive to port, positive up Distance from separation line in direction, m

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Section: Introductionmentioning

confidence: 99%

“…2 The typical noise generating mechanism of a landing gear is that of a compact dipole whose strength is proportional to the unsteady force exerted on the fluid by the component. 1,2 This mechanism is described by Curle's theory. 3 The directivity of landing gear noise is almost omni-directional at low Strouhal numbers.…”

Section: Introductionmentioning

confidence: 99%

Use of Blowing Flow Control to Reduce Bluff Body Interaction Noise

2012

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“…The reduced velocity can alleviate the flow impingement on the airfoil leading edge, hence attenuates the vortex-structure interaction. In such a way, the air blowing forms an "air curtain" in front of the airfoil, which has a similar effect as the passive control fairing used to reduce the landing gear noise (Dobrzynski et al, 2002;Li et al, 2012) by reducing the flow speed impinging upon the downstream components. Fig.…”

Section: Flow Field Measurementsmentioning

confidence: 99%

Experimental study of vortex–structure interaction noise radiated from rod–airfoil configurations

Wang

Chen

et al. 2014

Journal of Fluids and Structures

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“…More recently, a variety of control measures have been explored to help reduce the noise generation from the landing gear, most notably the use of fairings. [8][9][10] While the wheel assembly has been the focus of most of the noise control studies, little work has been done to identify and suppress the mechanism of noise generating from the assembly of the strut and the landing lights, even though it has been identified as a significant contributor to the overall noise emissions. [2] The objective of this investigation is to study the unsteady flow field and associated pressure fluctuations in the near-wake of the landing gear, focusing primarily on the effect of the spacing between the landing lights installed on the front landing gear.…”

Section: Introductionmentioning

confidence: 99%

The effect of proximity of the landing gear lights on its turbulent wake

Salt

Arežina

Lepore

et al. 2016

Journal of Turbulence

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A simplified model of a landing gear is tested in a wind tunnel to investigate the effect of the landing light location on the resulting noise generation. Examination of the near-field pressure fluctuations, combined with phase-locked stereoscopic particle imaging velocimetry of the unsteady wake identified two distinct sources of pressure fluctuations. The higher frequency source has a wide frequency band and is situated in the outer regions of the wake near the lights. On the other hand, the lower frequency source is found to be stronger, has a narrower frequency band and is developed further downstream in the wake, closer to the wake centreline. The lower frequency source is observed to be rather robust as it is hardly affected by the location of the landing lights, whereas the higher frequency source becomes weaker as the spacing between the lights is reduced. The effect of a splitter plate positioned downstream of the landing gear strut is also investigated as a means of reducing the lower frequency pressure fluctuations. Although the lower frequency source is considerably weakened by the splitter plate, substantial enhancement of the higher frequency source is observed.

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Research into Landing Gear Airframe Noise Reduction

Cited by 44 publications

References 2 publications

Use of Blowing Flow Control to Reduce Bluff Body Interaction Noise

Use of Blowing Flow Control to Reduce Bluff Body Interaction Noise

Experimental study of vortex–structure interaction noise radiated from rod–airfoil configurations

The effect of proximity of the landing gear lights on its turbulent wake

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