Airframe noise measurements in a large hard-walled closed-section wind tunnel

Marco, Alessandro Di; Burghignoli, Lorenzo; Centracchio, Francesco; Camussi, Roberto; Ahlefeldt, Thomas; Henning, Аrne; Müller, Jürg

doi:10.1016/j.apacoust.2018.11.006

Cited by 6 publications

(6 citation statements)

References 34 publications

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“…A further analysis of the reverberation effects was conducted to verify the reliability of the results obtained in the non-anechoic test section. Considering the size of the test section and the speed of sound, the estimate of the reflection times, assuming a source in the center of the wind tunnel, confirmed the absence of spurious effects in the processed data (see [36,37] for more details).…”

Section: The Wind Tunnel and The Modelmentioning

confidence: 62%

“…The conventional beamforming technique together with the diagonal removal and the spectral background noise subtraction ( [45]) provides sufficient SNR to eliminate background noise and reverberations in the closed test section ( [46,47]). More details are given in [36,37]. Furthermore, the noise sources obtained by applying traditional array processing methodologies are convolved with the point spread function (PSF), i.e., the array response to a unit source, whose shape depends on array geometry, size, and frequency (for more details, see [48]).…”

Section: Beamforming Methodologiesmentioning

confidence: 99%

“…The wind tunnel is normally used for aerodynamic measurements and is not optimized for noise measurements, although some validation measurements proved the suitability of the facility for acoustic measurements for industrial applications [38]. More recently, a validation test campaign in the same facility has been carried out by means of a loudspeaker, specifically designed to operate in the presence of flow and driven by several synthetic reference sounds [36,37]. A further analysis of the reverberation effects was conducted to verify the reliability of the results obtained in the non-anechoic test section.…”

Section: The Wind Tunnel and The Modelmentioning

confidence: 99%

“…Since each array position corresponded to a specific aircraft polar directivity angle, the latter feature was exploited to obtain useful information about the directivity of the noise sources. This methodology was successfully applied in the same facility using a known sound source as reference [36,37]. The information about source directivity characteristics is of further importance in view of potential applications such as the extrapolation of the effective perceived noise level (EPNL), which is required for the acoustic certification of civil aircraft.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of the noise impact of flap-tip fences installed on laminar wings

et al. 2020

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The aeroacoustics of laminar wings and the noise abatement provided by flap-tip fences are studied experimentally on a scaled model installed in the closed test section of a subsonic wind tunnel. The activity has been developed under an international project funded by the European Union through the H2020 Framework Program. The model reproduces an innovative regional aircraft mounting aft-engines and adopting the Natural Laminar Flow concept. Both take-off and landing settings are tested for several combinations of wind tunnel speeds and angles of attack; these configurations being the most critical from the viewpoint of airframe noise generation. A baseline configuration without flap-tip fences is also tested for a comparative study. Noise sources are identified by measuring pressure fluctuations through a phased microphone array. Data are processed using both Conventional Beamforming and CLEAN-SC algorithms to retrieve the sound source maps and the integrated spectra over the areas of interest. Directivity effects are investigated as well by moving the microphone array in different axial positions corresponding to different aircraft polar directivity angles. The wind tunnel data are eventually extrapolated to full scale and projected to flight condition allowing the analysis of the results in terms of Effective Perceived Noise Level (EPNL). Tests provided an extensive characterization of the acoustic behavior of the analyzed model demonstrating the capability of measurements carried out in a non-anechoic environment, to provide reliable data. The longitudinal traversing of the microphones array allowed us to compute, even though qualitatively, the EPNL and thus demonstrated the feasibility of a procedure that can be a reference for the design of future aeroacoustic tests. The effectiveness of the flap-tip fences to successfully reduce the flap side-edge noise has been definitely verified both through the analysis of the acoustic maps retrieved from the beamforming investigation and by the estimation of the overall variation of the EPNL with respect to a baseline reference configuration without low-noise devices.

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Section: The Wind Tunnel and The Modelmentioning

confidence: 62%

Section: Beamforming Methodologiesmentioning

confidence: 99%

Section: The Wind Tunnel and The Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Evaluation of the noise impact of flap-tip fences installed on laminar wings

et al. 2020

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“…At present, distortion theory has been used to solve the problem of incomplete similarity between the model and prototype in the dynamic investigation process of mechanical manufacture [7,8] and architecture design [9]; in addition, the design process and confirmation method of the scale model were also analyzed. Wang et al [10] confirmed the dynamic similarity relationship between the scale model and prototype in the design process of the circular plate; the model of thin wall part was designed to investigate the dynamic characteristics of the prototype [11] to solve the distortion problem of the thickness of the beam that cannot be adjusted by the same scale as the width in the QSCC scale model design process; the numerical correction method was presented to compensate the gap of experiment and simulation [12,13].…”

Section: Introductionmentioning

confidence: 99%

Design and Experimental Verification of a 1/20 Scale Model of Quayside Container Crane Using Distortion Theory

2019

Shock and Vibration

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The scale model is an effective method to research the performance of quayside container crane (QCC) under the seismic condition, but the model distortion usually exists in the similar design process which leads to the incomplete similarity between the scale model and prototype. In this investigation, the distortion theory and the prediction coefficient correction method are used to upgrade the quality of 1/20 QCC scale model and, then, the seismic response of the QCC prototype is obtained from the shake table scale model test. In the first step, the similarity ratio of the 1/20 QCC scale model is calculated by the similitude law and the size of scale model is obtained from the similarity constants. In the second step, the bending stiffness is selected and determined as the distortion term and, then, the relationship between the distortion coefficient and the prediction coefficient is obtained by the finite element prediction coefficient method. Furthermore, the three different scale models are manufactured and tested in the shake table experiment under different seismic conditions. It is found that the experimental test results are consistent with the numerical simulation results of the QCC prototype. It can be concluded that the QCC scale model can be used to predict the performance of the prototype under the different seismic conditions after corrected by distortion theory, and the distortion theory is an effective method to solve the incomplete similarity between the scale model and prototype.

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