Aerodynamic/Aeroacoustic testing in Anechoic Closed Test Sections of Low-Speed Wind Tunnels

Ito, Takeshi; Ura, Hiroki; Nakakita, Kazuyuki; Yokokawa, Yuzuru; Ng, Wing F.; Burdisso, Ricardo A.; Iwasaki, Akihito; Fujita, Tatsuhito; Ando, Norihisa; Shimada, Noriaki; Yamamoto, Kazuomi

doi:10.2514/6.2010-3750

Cited by 32 publications

(8 citation statements)

References 8 publications

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“…A photograph of the experimental setup is shown in Figure 1(a), a corresponding schematic in Figure 1(b). Similar setups are also used in other, often larger wind tunnel facilities [13][14][15].…”

Section: Iia Aeroacoustic Wind Tunnelmentioning

confidence: 94%

Flow Noise Generation of Cylinders with Soft Porous Cover

Geyer

Sarradj

Herold

2015

21st AIAA/CEAS Aeroacoustics Conference

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The use of porous materials is one of several approaches to control or minimize the generation of flow noise. As a simple model for struts and other protruding parts (for example components of the landing gear or pantographs from high speed trains), the noise generated by circular cylinders with a soft porous cover was measured in a small aeroacoustic wind tunnel at Reynolds numbers between approximately 16,000 and 103,000. The porous materials were characterized by their air flow resistivity, a parameter describing the permeability of an open-porous material. The aim of this study is to identify those materials that result in the best noise reduction, which refers to both tonal noise and broadband noise. To this end, measurements with single microphones were performed on a set of cylinders whose porous materials cover a large range of air flow resistivities.The results show that materials with low air flow resistivities lead to a noticeable flow noise reduction. Thereby, the main effect of the porous cylinder covers is that the spectral peak due to the aeolian tone is much narrower, but is not suppressed completely. Additionally, a reduction of broadband noise can be observed, especially at higher Reynolds numbers. The noise reduction increases with decreasing air flow resistivity of the porous covers, which means that materials that are highly permeable to air result in the best noise reduction. List of symbolsB [Hz] width of the spectral peak b [m] thickness of a sample of porous material D [m] outer diameter of the cylinders with porous cover d [m] diameter of the rigid core cylinder f [Hz] frequency Gmic1,mic2(f ) [Pa 2 /Hz] cross-spectral density between signals from microphone 1 and 2 Ma [-] Mach number L [m] length of the cylinders Lp [dB] sound pressure level Δp [Pa] static pressure difference r [Pa s/m 2 ] air flow resistivity of a porous material Re [-] Reynolds number based on cylinder diameter Sauto,mic1(f ) [Pa 2 /Hz] auto-spectral density of the signal from microphone 1 SCOP,mic1(f ) [Pa 2 /Hz] coherent noise spectral density from microphone 1 according to Equation (6) Sr [-] Strouhal number based on cylinder diameter Tu [%] turbulence intensity u [m/s] turbulent velocity fluctuations U [m/s] mean (time-averaged) flow velocity U0 [m/s] free stream velocity (flow speed) x, y, z [m] cartesian coordinates γ 2 mic1,mic2 (f ) [1] coherence between signals from microphone 1 and 2 σ [1] volume porosity τ [1] tortuosity

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Section: Iia Aeroacoustic Wind Tunnelmentioning

confidence: 94%

Flow Noise Generation of Cylinders with Soft Porous Cover

Geyer

Sarradj

Herold

2015

21st AIAA/CEAS Aeroacoustics Conference

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“…This section provides a brief description of the measurement details and the test section mounted in the aeroacoustic wind tunnel facility at the University of Bristol, including the Kevlar-walled test section, dynamic turntable, beamforming array, far-field microphone arc as well as the instrumented NACA 0012 airfoil. Kevlar-walled test sections are widely used in various anechoic wind tunnel facilities [26,27], in order to reduce the flow deflection, while enabling far-field noise measurements. The temperature-controlled aeroacoustic wind tunnel is anechoic for frequencies above 160 Hz, and was used with a nozzle with the exit dimensions of 500 mm in width and 775 mm in height.…”

Section: Methodsmentioning

confidence: 99%

Aeroacoustic investigation of an oscillating airfoil in the pre- and post-stall regime

Mayer

Zang

Azarpeyvand

2020

Aerospace Science and Technology

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The present study describes an experimental investigation of the aerodynamic and aeroacoustic characteristics of a sinusoidally oscillated NACA 0012 airfoil. The experiments were conducted in an aeroacoustic wind tunnel with a uniquely designed Kevlar-walled test section. Prior to experiments, these Kevlar walls were calibrated carefully and shown to provide reliable and accurate aerodynamic and aeroacoustic measurements. Two different regimes of interest, namely the pre-and post-stall angle of attack regimes, have been examined for lift curve polars, far-field noise spectra and unsteady surface pressure spectra. Interestingly, when the lift curve polar hysteresis is small at pre-stall angles of attack, the unsteady surface pressure spectra of the oscillating airfoil can be predicted with satisfactory accuracy using a position-based weighted averaging approach from its static counterparts. On the other hand, such a method becomes invalid at post-stall angles due to the presence of a significant dynamic stall hysteresis. Instead, an increase in the mean surface pressure and far-field noise spectra is observed at dynamic stall conditions. Furthermore, a short-time Fourier transform analysis reveals that the increase of the surface pressure spectra is a direct result of the periodic production and convection of dynamic stall vortices.

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“…JAXA has accumulated the experience in the wind tunnel tests for the slat noise. [13][14][15][16][17][18][19] At JAXA, the following wind tunnel measurements have been planned as part of a collaborative effort with NASA Langley Research Center to provide a portion of the dataset for Category 7 of the BANC workshops and, in general, an improved understanding and characterization of slat noise including the NBPs:…”

Section: Introductionmentioning

confidence: 99%