ACTA AERONAUTICAET ASTRONAUTICA SINICA >
Noise reduction mechanism of bionic airfoil trailing edge serrations
Received date: 2014-08-26
Revised date: 2015-03-25
Online published: 2015-04-09
Supported by
National Natural Science Foundation of China (51276149); State Key Laboratory of Aerodynamics Research Fund (SKLA20140201)
Large eddy simulation and acoustic analogy are performed to investigate the effects of trailing edge serrations on airfoil self-noise. A SD2030 airfoil is used for study. The trailing edge serrations' amplitude is 10% of airfoil chord while the serrations' wavelength is 4% of airfoil chord. The fluid field of SD2030 airfoil at 0° angle of attack with incoming flow velocity of 31 m/s is simulated and the corresponding Reynolds number based on airfoil chord is about 310 000.The effect of trailing edge serrations on the turbulence flow field near the airfoil trailing edge is analyzed in detail. Then FW-H equation is used to calculate the sound field of the straight/serrated trailing edge airfoil with the help of the sound source information obtained by the large eddy simulation. It is found that trailing edge serrations can significantly reduce airfoil noise in low to middle frequency range. The noise reduction can reach up to 16 dB in narrow band in the frequency range smaller than 4 000 Hz. However, the airfoil aerodynamic performance is adversely affected by the trailing edge serration. Further results show that the airfoil noise is dominated by laminar boundary layer-vortex shedding noise under the current condition. It is found that the trailing edge serrations can suppress the laminar boundary layer-vortex shedding phenomenon and reduce the surface pressure fluctuation near the airfoil trailing edge as well as airfoil lift fluctuation. In addition, the turbulent fluctuation at low frequency and the vorticity near the trailing edge are reduced. The vortex spanwise correlation is also decreased near the trailing edge. These factors work jointly and lead to the final airfoil self-noise reduction.
TONG Fan , QIAO Weiyang , WANG Liangfeng , JI Liang , WANG Xunnian . Noise reduction mechanism of bionic airfoil trailing edge serrations[J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2015 , 36(9) : 2911 -2922 . DOI: 10.7527/S1000-6893.2015.0084
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