qingkai wei, siyang zhong, xun huang · 2013. 8. 27. · supported by the national natural science...

Contact Information

Low Noise Aviation Lab, Peking University

Phone: 010-6275 8538

Email: huangxun@pku.edu.cn

Web: www.coe.pku.edu.cn/faculty/huangxun

Results

Experiment SetupA microphone array is used in an anechoic wind tunnel

with an open test section (the speed accuracy is within

± 0.1 m/s , 0.55 m × 0.4 m ) to yield noise source

images and characterize noise source spectra for a white

pigeon.

Experimental evaluation of flow-induced noise

in level flight of the pigeon (Columba livia)

BackgroundThe popularity of air traffic has led to serious

environmental issues in which noise is the most

distinguished issue for passengers and communities local

to airports. The development of high bypass ratio aero-

engine has the main contributor of aircraft noise moving

to the airframe for some modern transport aircrafts. Past

trends in aircraft noise reduction show that those

asymptotic improvements in airframe design might fail to

achieve the increasingly stringent regulations and the

public expectations.

Aviation researchers have been inspired by bird flight to

develop various aeronautic technologies. Avian wing

geometry and kinematic and aerodynamic mechanisms

have been extensively studied previously, particularly for

pigeons. Avian flight noise, however, is still an open

question, partially due to the absence of appropriate

testing methods.

Qingkai WEI, Siyang ZHONG, Xun HUANGState Key Laboratory of Turbulence and Complex Systems,

Department of Aeronautics and Astronautics, Peking University

AimPigeon’s level flight noise source images and characterize

noise source spectra can be given with a new experiment

method, which is different from those flyover noise

measurements and isolated dummy wing noise

measurements.

Future Work

3D real-time sound visualization method;

PIV or fluctuating pressure measurement on the wing;

Fluid mechanism of flexible flapping wing noise.

Acknowledgements

We thank Zhengwu Chen at China Aerodynamic Research and Development Center for his

care of the animal and the assistance in conducting these experiments. The work was

supported by the National Natural Science Foundation of China (No. 11172007) and

Science Foundation of Aeronautics of China (No. 20101271004).

2nd International Retreat on Vortex Dynamics and Vorticity Aerodynamics, Shanghai, August 15-17.

Array performance. (a) the layout of sensors; (b) photo of PKU

Array; (c) the associated array pattern at 3 kHz; (d) the signal-to-

noise ratio of the array. The live pigeon test results and preceding results (AIAA 2012-2230).

The experimental efforts can be largely eased off using isolated

dummy bird wing. However, the experimental accuracy using an

isolated wing of deceased birds needs justifications. (AIAA 2012-

2230)

Array Experiment setup. (a) The diagram of the experimental setup;

(b) image of the pigeon during the level flight at 𝑈∞ = 15 m/s.

The fly-over experiments capture flight noise mechanisms with high

confidence. However, it is very difficult to achieve a satisfactory

signal-to-noise ratio in those field tests. (AIAA J, Vol. 49, No. 4,

2011)

Acoustic image by Conventional Beamforming of the level flight at

𝑈∞ = 15 m/s, where the imaging frequency is (a) 2 kHz, (b) 3 kHz,

(c) 4 kHz, (d) 5 kHz, (e) 6 kHz, and (f) 7 kHz. The maximal sound

pressure value of each panel is normalized to 0 dB .

Acoustic image by DAMAS of the level flight at 𝑈∞ = 15 m/s, where

the imaging frequency is (a) 2 kHz, (b) 3 kHz, (c) 4 kHz, (d) 5 kHz, (e)

6 kHz, and (f) 7 kHz. The maximal sound pressure value of each panel

is normalized to 0 dB .

Some acoustic images of the pigeon’s level flight noise at

𝑈∞ = 15 m/s are shown, in which dynamic range is

10 dB, suggesting good quality of the experiments.

Dominant noise sources are at wing tips, which agrees

with the work by Geyer et al. (AIAA 2012-2230).

Sound strength is slightly asymmetrical because it is

difficulty to maintain perfectly horizontal level flight.

The spectral waveform of the pigeon flight suggests a

slope of −20 dB/dec between 500 Hz and 5 kHz.

A quantitative comparison:

the normalized SPL waveforms are almost the same at

low and middle frequency ranges;

our experiment are lower by a couple of decibels at

very high frequencies beyond 10 kHz.