Wind tunnel testing of porous devices for the reduction of flap side-edge noise in a 30P30N model (original) (raw)
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WIND TUNNEL TESTING OF POROUS DEVICES FOR THE REDUCTION OF FLAP SIDE-EDGE NOISE
This work investigates experimentally several flap side-edge treatments on a MD 30P30N wing model for noise reduction. The application of porous edges of various extensions, splitter plate were among the investigated treatments. The experiments were carried out in a solid wall low speed wind tunnel with turbulence level of 0.2% and capability of aeroacoustic testing with an overall SPL at 37m/s from 500 Hz to 20 kHz of 80 dB , with a peak 1/24 octave-band level of 75 dB at 500Hz that decreases to 67 dB at 2 kHz. The baseline configuration and those with side-edge treatments were tested and equivalent noise levels were obtained for low frequencies.
27TH INTERNATIONAL CONGRESS OF THE AERONAUTICAL SCIENCES
The present paper shows the results of the update of a previous aerodynamics wind-tunnel into a wind-tunnel with capacity to execute aeroacoustics tests, while keeping its good aerodynamic qualities. In order to reduce the wind tunnel background noise level, melamine foam was applied on wind-tunnel walls, and an acoustic baffle was installed between corner vane sections. Also a treatment was applied to the tip fan to the tip fan blades and the noise generated by the electric motor was insulated. Results showed a reduction of up to 5 dB and a noticeable removal of spectral tones after the wind-tunnel treatment. Another positive effect of the noise reduction was the decrease of test section turbulence, from its previous level of 0.25% to 0.21%. As a minor penalty, the insertion of noise treatment caused a maximum flow velocity maximum reduction of 2% for the same electric power input. All this process, described by the present paper, resulted on a wind-tunnel with good flow quality and capacity for aeroacoustics measurements.
EXPERIMENTAL ANALYSIS OF THE AERODYNAMICS OF POROUS FLAP SIDE-EDGE FOR NOISE REDUCTION
Experimental testes were carried out to investigate the flow near a flap side-edge with attached porous plate as a potential noise reduction device. The experiments were performed over a wing to simplify the installation. The objective was to perform a first approximation to the flow field produced by the addition of porosity of different sizes. Specifically, the changes in tip vortex were studied. Baseline case and plates of 10mm, 20mm, 30mm, 50mm and 70mm placed in the bottom side of the wing tip were tested. Also another configuration was tested, with a plate of 25mm roughly placed in the attachment line of the vortex. Aerodynamic experiments were performed to evaluate the changes in the lift, drag and pitching moment coefficients. Hot wire anemometry measurements were performed in perpendicular planes to the direction of the undisturbed flow. Problems in the calibration were detected, that corrupts all the values. Nevertheless, first results about the behavior of the flow field were achieved. The addition of the porous plate transforms the structure of the vortex by dramatically decreasing the axial velocity in the core center transforming the tip vortex from a jet vortex to a wake vortex. Vorticity was also changed with a noticeable decrease. From 30mm porous strip, this decrease becomes asymptotic. There are some structures that are not completely explained. The attachment line plate and the 10mm plate cases present a complex structure, which seems due to various vortices. The 50mm and 70mm plates show a merging between the wake and the vortex. The addition of the porous plate weakens the mechanisms of noise production. It is judged that this will lead to a noise reduction.
Flow-induced noise from wind tunnel turbulence reduction screens
11th Aeroacoustics Conference, 1987
Boeing is acquiring a new Low Speed Aeroacoustic Facility t o simulate low speed flight conditions by adding a f r c c jet t o an existing anechoic chamber. The primary facility characteristics will be high flow quality and l o w background noise levels in t h e open j e t t e s t section. During t h e design phase, it was recognized t h a t noise generated by flow through t h e turbulence reduction s c r e r n s could intrude on t h c t e s t section noise floor. Since no published information could b e found on flow noise i n screens, experiments were conducted t o measure flow noise far a wide variety of screen sizes 'and airflow velocities. Data analysis, using multiple regression, produced a screen noise prediction equation for overall sound power a s a function of flow velocity, scrcen wire diameter, number of screens, and screen cross-sectional area. This prediction should bc useful for wind tunncl design when low t e s t Section sound levels a r e required. Cop)rithl B .\meritan Inslitate or APronaalics and hsfronrutirs, Inc., 1987. All righlr r e s m e d .
The Update of an Aerodynamic Wind-Tunnel for Aeroacoustics Testing
Journal of Aerospace Technology and Management, 2014
This paper describes the update and characterization of a previously pure aerodynamics wind-tunnel into a facility able to simultaneously execute aerodynamics and aeroacoustics testing. It is demonstrated that the application of high-performance acoustic materials on strategic positions of the wind-tunnel circuit and punctual actions can substantially reduce the background-noise level. This paper shows efficient measures which resulted to broadband-noise reduction of up to 5 dB and practically complete removal of spectral tones. In addition, it is demonstrated that the applied acoustic treatment reduced the turbulence level, measured at the test-section at maximum operational velocity, from the previous 0.25% level to 0.21%. As a minor penalty, the acoustic treatment reduced the flow velocity in 2% for the same electric-power input. Finally, the work described in this paper resulted on a wind-tunnel with good flow quality and capacity for aeroacoustics testing.
Experimental and Numerical Aeroacoustic Analyses of a Large-scale Flap Side-edge Model
2019
In this research, the relationship between the parameters of a large-scale flap model and the physics responsible for flap side-edge noise generation, one of the most dominant sources of the airframe noise was investigated in experimental and computational tests. Flow-field measurements were taken according to phased microphone array techniques toward a deeper understanding of flap side-edge noise sources and their correlations to unsteady vorticity fluctuations. Conventional beamforming, CLEAN-SC and DAMAS methodologies provided far-field acoustic spectra estimations and noise source mapping, and numerical investigations were conducted by the commercial version of PowerFLOW 5.3 ®. The model used for the tests consists of an unswept isolated flap element with representative tip details present in a conventional medium-range transport aircraft. Different side-edge devices were assessed toward reductions in airframe noise. A perforated side-edge treatment was also applied to the flap side-edge. Aeroacoustic tests were conducted in the LAE-1 closed circuit wind tunnel with a closed working section at the São Carlos School of Engineering-University of São Paulo (EESC-USP) at up to 40 m/s flow speeds and the results provided specific information about the aeroacoustic characterization of the dominant acoustic source mechanisms of the flap model.
2007
Experimental investigation of flow-induced sound and sources of sound necessitates an adequate environment of low interfering noise and suppression of unwanted sources of sound. In order to investigate the sound from fluid-structure interactions, a low-noise wind tunnel has been designed and implemented. This paper gives an overview of the design criteria and specifications, along with an aeroacoustic and aerodynamic characterization of the facility. The suitability to airfoil self-noise studies is explored and first measurements with a model airfoil are presented. The paper concludes with suggestions for improvements and provides an outlook on future applications.
INCAS Bulletin, 2015
This book is addressed to researchers involved in projects related to Aerospace Sciences, and graduates from Aerospace Engineering, mainly, Mechanical Engineering, Transports Engineering and Civil Engineering as well. The book represents a synthesis of the authors experience with regard to the aerodynamic testing. Therefore, Jewel B. Barlow is a former chairman of the Subsonic Aerodynamic Testing Association (SATA) and former director of the University of Maryland's Glenn L. Martin Wind Tunnel, William H. Rae was associate director of the F. K. Kirsten Aeronautical Laboratory at the University of Washington and a charter member of the SATA, while Alan Pope was a Professor of Aeronautical Engineering at Georgia Tech, then former manager and director of the Aerodynamics Department at Sandia National Laboratories. Allan Pope has written other two reference books that can be mentioned: High-Speed Wind Tunnel Testing and Wind Tunnel Testing. The information covered in this book is structured in 18 chapters of a more than 700 A4 pages volume; each chapter is followed by explanatory notes; a useful list of numerical constants and conversion factors is provided in Appendix 2. The topics covered are: Chapter 1 introduces a part of the basic knowledge of aerodynamics and aeroacoustics (e.g. the properties of air and water, flow similarity, incompressible flow, time dependence of the solutions); the acquirement of such knowledge is considered to be relevant for the further wind tunnel testing. Chapters 2 and 3 provide a large amount of information regarding the wind tunnels and their design. For instance, in Chapter 2 is given a general presentation of the types of wind tunnels WT (e.g. aeronautical WT, aeroacoustic WT, general-purpose WT, environmental WT, as well as automobile WT, smoke tunnels and water tunnels). Chapter 3 is highly focused on the design of the wind tunnels; once the overall aerodynamic objectives being set, the design of the WT is customized, in accordance with the power considerations. Significant design details, as input data (e.g. section loss coefficients, energy ratios) and methodology (e.g. return diffuser, drive system, cooling, test section inserts, as well as safety) are also exposed. Chapter 4 is dedicated to the measurements of pressure, flow and shear stresses; the preparation and specific instrumentation, up to the flow field and surface analysis are detailed. The experiments are completed with the flow visualization methods and techniques presented within Chapter 5; path-lines, streak-lines, streamlines and timelines are defined