Numerical Investigation of a Realistic Nose Landing Gear

2018 AIAA/CEAS Aeroacoustics Conference

Snellen

et al. 2018

The noise emissions of a full-scale nose landing gear, measured in a wind tunnel and obtained from computational simulations, are compared with those of three regional aircraft types recorded in flyover measurements. The results from these three approaches are also compared with the predictions of two airframe noise models (Fink and Guo). The geometries of the nose landing gears in all cases were similar. Microphone arrays and acoustic imaging algorithms were employed to estimate the sound emissions of the nose landing gears. A good agreement was found between the overall trends of the frequency spectra in all cases. Moreover, the expected 6 th power law with the flow velocity was confirmed. On the other hand, strong tonal peaks (at around 2200 Hz) were only found for the flyover tests and computational simulations and are not present in typical noise prediction models. As the frequencies of the tones did not depend on the flow velocity, they are likely to be caused by cavities found in structural components of the nose landing gear. Removing these tones would cause overall noise reductions up to 2 dB in the frequency range examined. The noise emissions in the side direction did not present tonal peaks. The acoustic source maps showed that the dominant noise sources were located in the middle of the wheel axle, followed by the main strut and the bay doors. It is, therefore, recommended to further investigate this phenomenon, to include cavity-noise estimations in the current noise prediction models, and to eliminate such cavities where possible with the use of cavity caps, for example.

Section: Iic Computational Simulationsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Analysis of nose landing gear noise comparing numerical computations, prediction models and flyover and wind-tunnel measurements

Martinez

2018 AIAA/CEAS Aeroacoustics Conference

Snellen

et al. 2018

“…Hybrid methods, combining, for example, detached-eddy simulation [20] with the Ffowcs Williams-Hawkings analogy [21], allow realistic landing-gear models to be numerically modeled [22,23], and entirely different approaches using lattice Boltzmann methods [24] seem to be able to dramatically decrease computational times, allowing larger and larger models to be analyzed. However, these numerical methods and others are still in development and need to be validated against experimental results provided by dedicated datasets such as the Benchmark Problems for Airframe Noise Computations initiative [25].…”

Section: Introductionmentioning

confidence: 99%

Noise Characterization of a Full-Scale Nose Landing Gear

Bennett

Kennedy

2018

Journal of Aircraft

This paper presents experimental results from a nose landing-gear test campaign. A highly detailed model of the nose section of a 90-seat configuration green regional aircraft concept was built and tested in an aeroacoustic open-jet wind tunnel at full scale. All of the landing-gear components, fixtures, and small details and associated structures such as the complete wheel bay, bay doors, and hydraulic dressings were included at full scale. This paper focuses on one element of the testing: that of component noise assessment. The dressings, wheels, torque link, steering pinion, bay doors, and then the main strut and drag stay were removed in succession, and an acoustic evaluation was performed at a range of velocities from M 0.12 to M 0.19. In addition, hub caps were installed on the wheels, and their performance as a low-noise treatment is presented and assessed for efficacy. The landing gear, doors, and bay generated most noise in the frequency range between 120 and 400 Hz, but appreciable noise above the baseline was measured up to 10 kHz. The low-to midfrequency aerodynamic noise was found to scale with V 6 , as usual; however, the spectra at high frequencies collapsed perfectly when scaled to V 7 , confirming the fact that high-frequency noise is radiated from the turbulent flow surrounding small features. The total noise output of the landing-gear assembly differs from that of the sum of the components in isolation due to installation effects. The research in this paper studied these effects and the influence of the components on each other.

“…3. Computational simulations [33][34][35] of a detailed LG geometry can be very time-consuming due to its complex structure. On the other hand, extensive wind-tunnel or flyover test campaigns usually have a large economic cost, limiting the amount of configurations available for study.…”

mentioning

confidence: 99%

Multi-Approach Study of Nose Landing Gear Noise

Martinez

Snellen

et al. 2020

Journal of Aircraft

The noise emissions of a full-scale nose landing gear (NLG), measured in a wind tunnel and obtained from computational simulations, are compared with those of three regional aircraft types recorded in flyover measurements. A comparison is made with the noise prediction models of Fink, Guo, and DLR. A good agreement was found between all the spectra. The noise emissions up to 1.2 kHz were found to scale with the 6 th power of the flow velocity, as usual; however, the spectra at higher frequencies collapsed better when scaled to the 7 th power, confirming the fact that high-frequency noise is radiated from the turbulent flow surrounding small features of the NLG.