Visualization of aerodynamic noise source around a rotating fan blade

Abstract

The purpose of this study is to understand the aerodynamic noise source distribution around a rotating fan blade by measuring the noise signal and velocity field around the blade. The local noise-level distribution over the fan blade is measured by microphone arrays, and the flow field is visualized by smoke and phase-averaged PIV measurement. The noise source distribution is examined by cross-correlation analysis between noise signal and velocity fluctuation. It is found that the noise source is located near the rotating fan blade, especially around leading and trailing edges. The separation and reattachment of flow are observed near the leading edge, and the tip vortices and vortex shedding are found near the trailing edge. The cross-correlation distribution of the noise signal and the radial velocity fluctuation shows large magnitude in the correlated regions, which indicates the noise generation by the formation of vortex structure around the blade.

Numerical Investigation on the Aerodynamic and Aeroacoustic Characteristics in New Energy Vehicle Cooling Fan with Shroud

“…The aeroacoustic characteristics of cooling fans are determined by their aerodynamics, such as flow separation, secondary flow and other special flow structures. A large number of studies have been performed on aerodynamic characteristics [3][4][5][6][7][8][9] and aeroacoustic characteristics [10][11][12][13][14][15][16]. For example, Nashimoto et al [3] used phase-averaged PIV measurement and found that the separation and reattachment of the flow occurred on the suction surface at the leading edge of the blade.…”

“…A large number of studies have been performed on aerodynamic characteristics [3][4][5][6][7][8][9] and aeroacoustic characteristics [10][11][12][13][14][15][16]. For example, Nashimoto et al [3] used phase-averaged PIV measurement and found that the separation and reattachment of the flow occurred on the suction surface at the leading edge of the blade. Marcus et al [4] found that the clearance flow flows out of the clearance and then towards the blade, resulting in strong pressure fluctuations at the tip of the blade.…”

Reduction of aero-acoustic noise originating from a high-speed polygon mirror scanner motor in a laser beam printer utilizing air-flow analysis

“…They showed that the two-dimensional vortex method can predict the peak sound pressure levels from a centrifugal fan within a 4 dB-A deviation range of the measured sound. Nashimoto et al (2008) studied aerodynamic noise source distribution around a rotating blade by measuring the noise signal and velocity field around the blade. They showed that the noise signal closely correlates with velocity fluctuation, which indicates noise generation due to the formation of a vortex around the blade.…”

Aeroacoustic Investigations of a Leading Edge Slat by Means of the Causality Correlation Method

“…13 The causality correlation technique has been applied in the past by means of measuring the near-field fluctuations with various techniques. [13][14][15][16][17] Recent experiments [18][19][20][21][22][23] have shown that Particle-Image-Velocimetry (PIV) and microphone measurements can be used to obtain the cross correlation function between a near-field quantity and the acoustic pressure in the far-field. Using of the technique for the application orientated flow field around a slat presented here is the next step in the development of the causality correlation by means of PIV measurements in the near-field.…”