Suppression of Wind Tunnel Buffeting by Active Flow Control

Heesen, Wilhelm von; Höpfer, Matthias

doi:10.4271/2004-01-0805

Cited by 18 publications

(19 citation statements)

References 15 publications

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“…Low-and high-pass filters with cutoff frequencies of 30 kHz and 5 Hz, respectively, were used. The low-pass filter was applied during the data acquisition to avoid aliasing and the high-pass filter was applied during the postprocessing to remove from the signal the effect of flow buffeting instability present in OTS wind tunnels [39] with direct influence on the length scale calculation. This same methodology was adopted in the lateral length scale measurements described in the following subsection.…”

Section: Turbulence Developmentmentioning

confidence: 99%

Modeling the Turbulence Spectrum Dissipation Range for Leading-Edge Noise Prediction

et al. 2022

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Noise pollution caused by inflow turbulence is a major problem in many applications, e.g., propellers and fans. The Amiet leading-edge noise prediction model is widely applied in the design of silent propellers and fans, strongly relying on the accuracy of the inflow turbulence spectrum. The von Kármán energy spectrum accurately models the energy-containing range and inertial subrange of the turbulence spectrum. However, this model does not incorporate the dissipation range of the turbulent energy and leads to incorrect far-field noise estimates in the high-frequency range. In this study, empirical formulations are presented for the dissipation frequency and the dissipation range based on experimental data. Two passive grids were used to generate nearly isotropic inflow turbulence, which was characterized by hot-wire anemometry. These results showed that the dissipation frequency depends on the intensity of the velocity fluctuations and on the freestream velocity. The expressions proposed to predict the dissipation frequency and the dissipation range had a fairly good agreement with the measured data in this research and with experimental data from the literature. The predicted leading-edge noise is significantly affected by the dissipation range, causing a decrease in level of up to 17 dB for the highest frequencies.

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Section: Turbulence Developmentmentioning

confidence: 99%

Modeling the Turbulence Spectrum Dissipation Range for Leading-Edge Noise Prediction

et al. 2022

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“…The data was recorded for 30 s with a sampling frequency of 65,536 Hz and a low-pass filter with a cut-off frequency of 30 kHz. A high-pass filter with a cut-off frequency of 5 Hz was used during the post-processing to eliminate the effect of the flow buffeting instability naturally present in an open test section wind tunnel [37], which has a direct influence on the length scale calculation. The hot-wire measurements were performed for 𝑅𝑒 = {2.0, 4.0, 6.0} × 10 5 for the grid-generated turbulence and 𝑅𝑒 = {3.0, 4.8, 6.4} × 10 5 for the rod-generated turbulence.…”

Section: Hot-wire Measurementsmentioning

confidence: 99%

On the turbulence distortion effects for airfoil leading-edge noise prediction

Santos

Botero

Venner

et al. 2022

28th AIAA/CEAS Aeroacoustics 2022 Conference

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Amiet's leading-edge noise prediction model estimates the noise generated by the turbulent inflow interacting with the leading-edge (LE) of an airfoil. Although successful in predicting the noise of thin flat plates, Amiet's model does not account for the real airfoil geometry, resulting in inaccurate noise estimation for these geometries. For real airfoils, turbulence distortion is an important but not entirely understood phenomenon that affects the airfoil radiated noise. This paper discusses the turbulence distortion in the vicinity of an airfoil LE focusing on improving Amiet's noise prediction. Experiments were performed in the Aeroacoustic Wind Tunnel of the University of Twente. The inflow turbulence was generated by a grid and a circular rod, and it was evaluated in the vicinity of a NACA 0008 airfoil LE using hot-wire anemometry and wall-pressure fluctuation measurements. The chord-based Reynolds number ranged from 2 × 10 5 to 6.4 × 10 5 . The rod-airfoil radiated noise was measured and compared with Amiet's model. Results show that the root-mean-square of the velocity fluctuations, 𝒖 𝒓 𝒎𝒔 , and the turbulence integral length scale, 𝚲 𝒇 , at the stagnation line considerably decreased as the LE is approached. The radiated LE noise predicted by Amiet's model overestimates the LE noise for high frequencies. However, the predicted LE noise agrees well with the measurements up to a Strouhal number of 10 if the turbulence spectrum based on the rapid distortion theory is used in Amiet's model, with input the 𝒖 𝒓 𝒎𝒔 and 𝚲 𝒇 values measured close to the airfoil LE. This shows that the turbulence distortion can be accounted for in the LE noise prediction model. This paper also provides empirical expressions for 𝒖 𝒓 𝒎𝒔 and 𝚲 𝒇 in the vicinity of the airfoil LE. These expressions yield more accurate noise predictions for low and high frequencies with Amiet's method.

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“…Efforts to understand the physics and to reduce the impact of those low frequency fluctuations on data quality and wind tunnel operation have been reported in many recent technical papers (Arnette and Buchanan, 1999;Wickern et al, 2000;Rennie et al, 2004;von Heesen and Höpfer, 2000).…”

Section: Introductionmentioning

confidence: 99%