Estimation of the far-field directivity of broadband aeroengine fan noise using an in-duct axial microphone array

2010 ◽  
Vol 329 (19) ◽  
pp. 3940-3957 ◽  
Author(s):  
C.R. Lowis ◽  
P.F. Joseph ◽  
A.J. Kempton
Keyword(s):  
Microphone Array ◽  
Far Field ◽  
Fan Noise

Far-Field Noise Control in Supersonic Jets From Conical and Contoured Nozzles

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Jin-Hwa Kim ◽  
Martin Kearney-Fischer ◽  
Mo Samimy ◽  
Sivaram Gogineni
Keyword(s):  
Sound Pressure ◽  
Acoustic Noise ◽  
Microphone Array ◽  
Plasma Actuators ◽  
Far Field ◽  
Free Jet ◽  
Naturally Occurring ◽  
Mixing Noise ◽  
Field Noise ◽  
Jet Axis

Plasma actuators are used to control far-field noise in Mach 1.65 jets from contoured and conical supersonic axisymmetric nozzles (henceforth, contoured and conical jets, respectively). The contoured nozzle is designed using the method of characteristics for a shock-free jet. The conical nozzle has converging and diverging conical sections with a sharp throat. Eight plasma actuators, distributed uniformly around the nozzle exit, are used and the jet is forced with azimuthal modes (m) 0–3 and ±4 and forcing Strouhal numbers ranging from 0.09 to 4.0. The far-field acoustic noise is measured by a linear microphone array covering polar angles from 25 deg to 80 deg relative to the jet axis. In both jets, the lower forcing azimuthal modes (m=0 and 1) are less effective than the higher modes (m=2, 3, and ±4), which have similar levels of overall sound pressure level (OASPL) reduction. At shallow angles relative to the jet axis, the reduction in OASPL is about 1.6–1.8 dB at low forcing Strouhal numbers in both jets at the most effective forcing mode of m=3. However, the OASPL in the sideline direction is only slightly increased (about 1 dB) for both the contoured and conical jets at m=3. The reduction at shallow polar angles is related to the decrease in the peak mixing noise level in both jets. The range of forcing Strouhal numbers providing significant noise reduction and the range of polar angles over which the noise is reduced are both much larger in the conical jet compared with the contoured jet. The screech tones are also reduced or suppressed – most likely due to weakening of naturally occurring structures by forcing.

A beamforming paradox: Using far‐field techniques to design a near‐field microphone array

1997 ◽  
Vol 102 (5) ◽  
pp. 3208-3208
Author(s):  
Darren B. Ward ◽  
Rodney A. Kennedy ◽  
Thushara Abhayapala
Keyword(s):  
Microphone Array ◽  
Near Field ◽  
Far Field ◽  
Field Techniques

Noise Characteristics of Automobile Cooling Fan Based on Circumferential Mode Analysis

2021 ◽  
Author(s):  
Pengfei Chai ◽  
Zonghan Sun ◽  
Zhiqiang Chang ◽  
Zhigang Peng ◽  
Jie Tian ◽  
...  
Keyword(s):  
Automobile Industry ◽  
Cooling System ◽  
Tip Clearance ◽  
Mode Analysis ◽  
Far Field ◽  
Axial Fan ◽  
Fan Noise ◽  
Cooling Fan ◽  
Noise Characteristics ◽  
Cooling Fans

Abstract The fan is the main component of the cooling system of an automobile engine. A typical automobile cooling fan consists of a shrouded axial fan, stator vanes, a deflector, and a cover. With recent developments in the automobile industry, the increase in the speed of rotation and blade load of cooling fans has increased the noise generated by them. To reduce it, it is important to analyze the characteristics of this noise. This paper uses an acoustic test to examine the characteristics of flow and noise of automobile cooling fans. The frequency spectrum and far-field radiation of the noise of the fan are first analyzed through far-field measurements, and the influence of the single rotor, tip clearance of the blade, and cover on fan noise is studied. The distribution of the mode spectrum and characteristics of sound propagation of discrete tonal noise are then examined using the circumferential mode test. The influence of the flow structure on fan noise is also studied. The flow characteristics and distribution of the source of noise of the automobile cooling fan are then used to analyze the influence of the structure of the fan on the noise generated by it. The results can help develop designs to reduce the noise of automobile cooling fans.

Noise Characteristics of Automobile Cooling Fan Based On Circumferential Mode Analysis

2021 ◽  
Author(s):  
Pengfei Chai ◽  
Zonghan Sun ◽  
Zhiqiang Chang ◽  
Zhigang Peng ◽  
Jie Tian ◽  
...  
Keyword(s):  
Automobile Industry ◽  
Cooling System ◽  
Tip Clearance ◽  
Mode Analysis ◽  
Far Field ◽  
Axial Fan ◽  
Fan Noise ◽  
Cooling Fan ◽  
Noise Characteristics ◽  
Cooling Fans

Abstract The fan is the main component of the cooling system of an automobile engine. A typical automobile cooling fan consists of a shrouded axial fan, stator vanes, a deflector, and a cover. With recent developments in the automobile industry, the increase in the speed of rotation and blade load of cooling fans has increased the noise generated by them. To reduce it, it is important to analyze the characteristics of this noise. This paper uses an acoustic test to examine the characteristics of flow and noise of automobile cooling fans. The frequency spectrum and far-field radiation of the noise of the fan are first analyzed through far-field measurements, and the influence of the single rotor, tip clearance of the blade, and cover on fan noise is studied. The distribution of the mode spectrum and characteristics of sound propagation of discrete tonal noise are then examined using the circumferential mode test. The influence of the flow structure on fan noise is also studied. The flow characteristics and distribution of the source of noise of the automobile cooling fan are then used to analyze the influence of the structure of the fan on the noise generated by it. The results can help develop designs to reduce the noise of automobile cooling fans.

Far-field measurement and mode analysis of the effects of vane/bladeratio on fan noise

1984 ◽  
Author(s):  
P. SCHWALLER ◽  
A. PARRY ◽  
M. OLIVER ◽  
A. ECCLESTON
Keyword(s):  
Field Measurement ◽  
Mode Analysis ◽  
Far Field ◽  
Fan Noise

Fan Noise Source Diagnostic Test -- Far-field Acoustic Results

2002 ◽  
Author(s):  
Richard Woodward ◽  
Christopher Hughes ◽  
Robert Jeracki ◽  
Christopher Miller
Keyword(s):  
Diagnostic Test ◽  
Noise Source ◽  
Far Field ◽  
Fan Noise

On the prediction of far-field fan noise attenuation due to liners considering uniform and shear flows

2018 ◽  
Author(s):  
Danilo S. Braga ◽  
Andre Spillere ◽  
Julio A. Cordioli ◽  
Andrey R. da Silva ◽  
Danillo C. Reis
Keyword(s):  
Shear Flows ◽  
Far Field ◽  
Noise Attenuation ◽  
Fan Noise

Integrated “CFD - Acoustic” Computational Approach to the Simulation of Aircraft Fan Noise

2014 ◽  
Author(s):  
Piergiorgio Ferrante ◽  
Paolo di Francescantonio ◽  
Pierre-Alain Hoffer ◽  
Stéphane Vilmin ◽  
Charles Hirsch
Keyword(s):  
Unsteady Flow ◽  
Sound Propagation ◽  
Noise Source ◽  
Acoustic Radiation ◽  
Near Field ◽  
Sound Field ◽  
Computational Approach ◽  
Far Field ◽  
Fan Noise ◽  
Field Noise

An innovative computational approach, integrating mesh generation, CFD simultaneous analysis of noise source and propagation, with acoustic radiation, is presented and applied to the simulation of the Advanced Noise Control Fan (ANCF) developed by NASA Glenn Research Center. The tonal noise source and the sound propagation in the nacelle duct and in the nacelle near field are simultaneously predicted, starting from the engine geometry and parameters, with a single CFD analysis based on an efficient Nonlinear Harmonic (NLH) method. The sound radiation to the far field is computed with the Green’s function approach implemented in a BEM frequency domain solver of the convective Helmholtz equation. The present method provides to a gain of close to two orders of magnitude compared to standard approaches, based on full unsteady flow simulations, followed by a near-field FEM based approach and a BEM method for the far-field noise propagation. The final comparison between the numerical results and the measurements highlights the capability of the methodology to efficiently predict the unsteady flow field and the radiated sound field.

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