Measurement of tonal-noise characteristics and periodic flow structure around NACA0018 airfoil

The characteristics of tonal noise and the variations of flow structure around NACA0018 airfoil in a uniform flow are studied by means of simultaneous measurement of noise and velocity field by particle-image velocimetry to understand the generation mechanism of tonal noise. Measurements are made on the noise characteristics, the phase-averaged velocity field with respect to the noise signal, and the cross-correlation contour of velocity fluctuations and noise signal. These experimental results indicate that the tonal noise is generated from the periodic vortex structure on the pressure surface of the airfoil near the trailing edge of the airfoil. It is found that the vortex structure is highly correlated with the noise signal, which indicates the presence of noise-source distribution on the pressure surface. The vorticity distribution on the pressure surface breaks down near the trailing edge of the airfoil and forms a staggered vortex street in the wake of the airfoil.

[1]  S. E. Wright,et al.  The acoustic spectrum of axial flow machines , 1975 .

[2]  M. S. Howe.  A review of the theory of trailing edge noise , 1978 .

[3]  N. Fujisawa,et al.  Evaluation of pressure field and fluid forces on a circular cylinder with and without rotational oscillation using velocity data from PIV measurement , 2005 .

[4]  Andreas Schröder,et al.  Particle image velocimetry in aerodynamics: Technology and applications in wind tunnels , 1999 .

[5]  徹 深野,et al.  Relationship between Wake Vortex Formation and Discrete Frequency Noise in NACA Blades , 1995 .

[6]  Alan McAlpine,et al.  Boundary-layer instability noise on aerofoils , 1999, Journal of Fluid Mechanics.

[7]  Christopher K. W. Tam,et al.  Discrete tones of isolated airfoils , 1974 .

[8]  N. Fujisawa,et al.  Computation of unsteady flow and aerodynamic noise of NACA0018 airfoil using large-eddy simulation , 2006 .

[9]  N. Fujisawa,et al.  Flow control around a circular cylinder by internal acoustic excitation , 2003 .

[10]  Martin R. Fink,et al.  Vortex Noise of Isolated Airfoils , 1972 .

[11]  Pierre Sagaut,et al.  Trailing-Edge Noise Prediction Using Large-Eddy Simulation and Acoustic Analogy , 2000 .

[12]  L. Lourenço.  Particle Image Velocimetry , 1989 .

[13]  P. Moin,et al.  Computation of Trailing-Edge Flow and Noise Using Large-Eddy Simulation , 2000 .

[14]  R. E. Longhouse.  Vortex shedding noise of low tip speed, axial flow fans , 1977 .

[15]  Alan McAlpine,et al.  On the Generation of Discrete Frequency Tones by the Flow around an Aerofoil , 1999 .

[16]  S. Lee,et al.  A Study on Discrete Frequency Noise from a Symmetrical Airfoil in a Uniform Flow , 2002 .

[17]  Chiang Shih,et al.  Investigation of flow at leading and trailing edges of pitching-up airfoil , 1995 .

[18]  H. Arbey,et al.  Noise generated by airfoil profiles placed in a uniform laminar flow , 1983, Journal of Fluid Mechanics.

[19]  Nobuyuki Fujisawa,et al.  Measurement of aerodynamic noise and unsteady flow field around a symmetrical airfoil , 2002 .

[20]  Michel Roger,et al.  Broadband Self Noise from Loaded Fan Blades , 2004 .

[21]  S. Akishita,et al.  Tone-like noise from an isolated two dimensional airfoil , 1986 .

[22]  Nobuyuki Fujisawa,et al.  An uncertainty analysis of temperature and velocity measured by a liquid crystal visualization technique , 2001 .