Broadband noise generation by aerofoils and axial flow fans

1973 ◽  
Author(s):  
B. MUGRIDGE
Keyword(s):  
Axial Flow ◽  
Broadband Noise ◽  
Noise Generation

Discrete Frequency Noise Generation From an Axial Flow Fan Blade Row

1970 ◽  
Vol 92 (1) ◽  
pp. 37-43 ◽  
Author(s):  
Ramani Mani
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Acoustic Energy ◽  
Frequency Noise ◽  
Noise Generation ◽  
Two Dimensional ◽  
Axial Flow Fan ◽  
Fan Noise ◽  
Blade Row ◽  
Fan Blade

An analysis is presented which treats the noise generation from an axial flow fan row by given forces including the effects of a moving medium. The linearization of Euler’s equations to yield tractable problems for fan noise is discussed. The three-dimensional problem is decomposed into several two-dimensional problems. Finally, full details are given of a two-dimensional analysis to predict the amounts of acoustic energy, at the blade passing frequency and its harmonics, radiated up and downstream of a blade row due to its interaction with a neighboring row.

Broadband Noise Generation by a Vortex Model of Cavity Flow

AIAA Journal ◽  
1977 ◽  
Vol 15 (5) ◽  
pp. 632-637 ◽  
Author(s):  
Jay C. Hardin ◽  
Jean P. Mason
Keyword(s):  
Cavity Flow ◽  
Broadband Noise ◽  
Noise Generation ◽  
Vortex Model

Noise generation in vane axial fans due to rotating stall and surge

2001 ◽  
Vol 215 (1) ◽  
pp. 57-64 ◽  
Author(s):  
M Čudina
Keyword(s):  
Rotor Blade ◽  
Guide Vane ◽  
Axial Flow ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Noise Generation ◽  
Total Noise ◽  
Operating Stability ◽  
Partial Load ◽  
Axial Fans

A characteristic of axial flow fans is instabilities in their performance and noise in partial load operation. These instabilities are a consequence of rotating stall created in the rotor blade and/or in the guide vane cascade. At some operating conditions the rotating stall caused the appearance of a surge representing the lowest region of fan operating stability. The rotating stall and especially surge caused a steep increase in the emitted noise and lowered the performance of the fan. The present paper highlights the rotating stall generation phenomenon and its influence on the emitted total noise level and noise spectra for axial flow fans with inlet and outlet guide vanes.

Noise generation in axial flow fans

1966 ◽  
Vol 3 (1) ◽  
pp. 46-56 ◽  
Author(s):  
C.G. van Niekerk
Keyword(s):  
Axial Flow ◽  
Noise Generation

scholarly journals Trailing Edge Thickness Effect on Tonal Noise Emission Characteristics from Wind Turbine Blades

2021 ◽  
Vol 13 (4) ◽  
pp. 99-111
Author(s):  
Satya Prasad MADDULA ◽  
Vasishta Bhargava NUKALA ◽  
Venkata Swamy Naidu NEIGAPULA
Keyword(s):  
Wind Turbine ◽  
Power Level ◽  
Turbine Blades ◽  
Broadband Noise ◽  
Thickness Effect ◽  
Sound Power ◽  
Noise Generation ◽  
Wind Turbine Blades ◽  
Trailing Edge ◽  
Sound Power Level

Broadband noise generation from wind turbine blades is one of the fundamental aspects of flow-induced noise. Besides the turbulent boundary layer flow over the blades, factors such as the angle of attack, the turbulence intensity, the trailing edge thickness of the blade and their shapes strongly influence the overall sound power levels at high frequencies, i.e. f > 8 kHz. In large operating wind farms, a trade-off between noise generation and power production is considered by power utility firms to maximize the return on investment (ROI) and minimize the fatigue damage on wind turbine components. The present work deals with the analysis of the thickness effect on trailing edge bluntness noise level at hub height average wind speeds of 7 m/s, 10 m/s. A semi-empirical BPM model was used to predict the sound pressure levels from the 37 m blade length of a 2MW wind turbine. The receiver configuration was fixed at a distance of 120 m from the source height of 80 m. The results demonstrated that as the trailing edge height increased from 0.1 % to 0.5 % of the local chord, the sound power level increased by ~ 17 dB for frequencies > 200 Hz, but decreased by 16 dB when the thickness is 0.1 % local chord. The computed results of the sound power level using the BPM model have been validated using experimental data and showed a good agreement for the tonal frequencies, f ~ 10 kHz, where the trailing edge bluntness noise becomes dominant.

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