Two-step computational aeroacoustics approach for underhood cooling fan application

2021 ◽  
Vol 263 (3) ◽  
pp. 3615-3624
Author(s):  
Parag Chaudhari ◽  
Jose Magalhaes ◽  
Aparna Salunkhe
Keyword(s):  
Flow Field ◽  
Sound Pressure ◽  
Acoustic Analysis ◽  
Air Flow ◽  
Computational Aeroacoustics ◽  
Noise Sources ◽  
Fan Noise ◽  
Cooling Fan ◽  
Sound Pressure Levels ◽  
One Step

Aeroacoustic noise is one of the important characteristics of the fan design. Computational Aeroacoustics (CAA) can provide better design options without relying on physical prototypes and reduce the development time and cost. There are two ways of performing CAA analysis; one-step and two-step approach. In one-step CAA, air flow and acoustic analysis are carried out in a single software. In two-step approach, air flow and acoustic analysis are carried out in separate software. Two-step CAA approach can expedite the calculation process and can be implemented in larger and complex domain problems. For the work presented in this paper, a mockup of an underhood cooling fan was designed. The sound pressure levels were measured for different installation configurations. The sound pressure level for one of the configurations was calculated with two-step approach and compared with test data. The compressible fluid flow field was first computed in a commercially available computational fluid dynamics software. This flow field was imported in a separate software where fan noise sources were computed and further used to predict the sound pressure levels at various microphone locations. The results show an excellent correlation between test and simulation for both tonal and broadband components of the fan noise.

Development of an Ultra-Quiet Fan for Computer Cooling Applications

2014 ◽  
Author(s):  
Zhenyu Wang ◽  
Hui Hu
Keyword(s):  
Flow Field ◽  
Noise Reduction ◽  
Sound Pressure ◽  
Field Measurements ◽  
Vortex Structures ◽  
Tip Clearance ◽  
Axial Fan ◽  
Fan Noise ◽  
Piv Measurements ◽  
Cooling Fan

We report the progress made in our recent study to develop an ultra-quiet axial fan for computer cooling applications. By using a commercially-available cooling fan as the baseline, a number of acoustically tailored modifications are implemented in order to reduce the noise level of the cooling fan, which includes optimizing the rotator blades and guide vanes according to axial fan design theory, adding an intake cone in the front of the hub to guide the airflow into the axial fan smoothly, and reducing the tip clearance to lower the noise generation due to tip vortex structures. A comparison study is conducted to measure the sound pressure level (SPL) of the reformed axial fan in an anechoic chamber, in comparison to that of the prototype fan, in order to assess the effects of the modifications on the fan noise reduction. The measurement results of our preliminary study reveal that, at the same flow rate, the SPL of the reformed fan would be up to 5 dB lower than that of the prototype fan. In addition to measuring the sound pressure levels (SPLs) of the fans, a digital particle image velocimetry (PIV) system is also used to conduct detailed flow field measurements to reveal the changes of the flow characteristics and unsteady vortex structures associated with the modifications. Besides conducting “free-run” PIV measurements to determine the ensemble-averaged statistics of the flow quantities such as mean velocity, Reynolds stress, and turbulence kinetic energy (TKE) distributions at the exit of the axial fan, “phase-locked” PIV measurements are also performed to elucidate further details about evolution of the unsteady vortex structures in fan exhaust in relation to the position of the rotating fan blades. The detailed flow field measurements are correlated with the SPL measurements in order to elucidate underlying physics associated with the fan noise reduction.

An Experimental and Computational Study on the Aerodynamic and Acoustic Characteristics of Case Fans

2015 ◽  
Author(s):  
Zhenyu Wang ◽  
Hui Hu
Keyword(s):  
Flow Field ◽  
Noise Reduction ◽  
Sound Pressure ◽  
Numerical Study ◽  
Field Measurements ◽  
Vortex Structures ◽  
Tip Clearance ◽  
Axial Fan ◽  
Fan Noise ◽  
Cooling Fan

We report the progress made in our recent study to develop an ultra-quiet axial fan for computer cooling applications. By using a commercially-available cooling fan as the baseline, a number of acoustically tailored modifications are implemented in order to reduce the noise level of the cooling fan, which includes optimizing the rotating blades and guide vanes according to axial fan design theory, adding an intake cone in the front of the hub to guide the airflow into the axial fan smoothly, and reducing the tip clearance to lower the noise generation due to tip vortex structures. A comparison study is conducted to measure the sound pressure level (SPL) of the new-design axial fan in an anechoic chamber, in comparison to that of the baseline fan, in order to assess the effects of the modifications on the fan noise reduction. The measurement results of our study reveal that, at the same flow rate, the SPL of the new-design fan would be up to 5 dB lower than that of the baseline fan. In addition to measuring the sound pressure levels (SPLs) of the fans, a digital particle image velocimetry (PIV) system is also used to conduct detailed flow field measurements to reveal the changes of the flow characteristics and unsteady vortex structures associated with the modifications. “Time-averaged” PIV measurements illustrate the ensemble-averaged statistics of the flow quantities such as mean velocity, Reynolds stress, and turbulence kinetic energy (TKE) distributions at the flow field around the axial fan. Moreover, a numerical study of the new-design fan is also performed and which is aimed to investigate the flow details inside of the fan. The validation comparison between numerical results and experimental results agree very well and that gives the strong confidence for the computational flow field in the fan can be regarded as useful complement for experiments. The detailed flow field measurements are correlated with the SPL measurements in order to elucidate underlying physics associated with the fan noise reduction.

Assessment of Environmental Noise and Air Quality in Critical Areas at UiTM Engineering Complex

2013 ◽  
Vol 471 ◽  
pp. 125-129
Author(s):  
N.V. David ◽  
K. Ismail
Keyword(s):  
Air Quality ◽  
Sound Pressure ◽  
Quality Measurement ◽  
Environmental Noise ◽  
Sound Level ◽  
Public Parks ◽  
Noise Sources ◽  
Critical Areas ◽  
Sound Levels ◽  
Sound Pressure Levels

Excessive environmental noise and poor air quality can be adverse to human health, living comfort and the environment itself. Measurement of sound pressure levels and air quality in critical areas including libraries, campus areas, public parks and hospitals thus becomes necessary to monitor and mitigate existing noise levels. In a university environment, student activities will be less disrupted if the locations of the activities are sufficiently away from noise sources. The present study is intended to measure sound levels and air quality around the Engineering Complex, Universiti Teknologi Mara, Shah Alam. The measured data is compared with to acceptable sound pressure levels and air quality index specified by the Department of Environment (DOE), Malaysia. Sound pressure levels are measured using the Castle Sound Level Meter Type 6224 and air quality measurement was done by using the BW Gas Alert MicroClip XT device. Both measurements were conducted at five selected stations around the Engineering Complex for three times each weekday for five weeks. Results obtained indicated that sound levels at some locations and time zones are above the thresholds recommended by the DOE. The air quality is acceptable in most locations except the vicinity of a bus stop. With the growing number of students in the university and other factors like construction and redevelopment of existing roads, a continuously increasing noise situations and air pollution proportional to the traffic flow is inevitable.

scholarly journals Prediction and Reduction of Aerodynamic Noise of the Multiblade Centrifugal Fan

2014 ◽  
Vol 6 ◽  
pp. 712421 ◽  
Author(s):  
Shuiqing Zhou ◽  
Jun Wang
Keyword(s):  
Flow Field ◽  
Sound Pressure ◽  
Acoustic Analysis ◽  
Low Noise ◽  
Aerodynamic Noise ◽  
Hybrid Technique ◽  
Field Calculation ◽  
Pressure Amplitude ◽  
Centrifugal Fan ◽  
Hybrid Techniques

An aerodynamic and aeroacoustic investigation of the multiblade centrifugal fan is proposed in this paper, and a hybrid technique of combining flow field calculation and acoustic analysis is applied to solve the aeroacoustic problem of multiblade centrifugal fan. The unsteady flow field of the multiblade centrifugal fan is predicted by solving the incompressible Reynolds-averaged Navier-Stokes (RANS) equations with conventional computing techniques for fluid dynamics. The principal noise source induced is extracted from the calculation of the flow field by using acoustic principles, and the modeled sources on inner and outer surfaces of the volute are calculated with multiregional boundary element method (BEM). Through qualitative analysis, the sound pressure amplitude distribution of the multiblade centrifugal fan in near field is given and the sound pressure level (SPL) spectrum diagram of monitoring points in far field is obtained. Based on the analysis results, the volute tongue structure is adjusted and then a low-noise design for the centrifugal fan is proposed. The comparison of noise tests shows the noise reduction of improved fan model is more obvious, which is in good agreement with the prediction using the hybrid techniques.

A NOTE ON "COMPUTATIONAL AEROACOUSTICS EXAMPLES SHOWING THE FAILURE OF THE ACOUSTIC ANALOGY THEORY TO IDENTIFY THE CORRECT NOISE SOURCES" BY CKW TAM

2004 ◽  
Vol 12 (04) ◽  
pp. 631-634 ◽  
Author(s):  
N. PEAKE
Keyword(s):  
Flow Field ◽  
Euler Equations ◽  
Normal Shock ◽  
Simple Problem ◽  
Computational Aeroacoustics ◽  
Acoustic Analogy ◽  
Noise Sources ◽  
Exact Agreement

In a recent paper (J. Computational Acoustics10 (2002) 387–405) Tam has claimed that the famous Lighthill Acoustic Analogy predicts the wrong flow field for the simple problem of the propagation of a normal shock. However, we show that Tam has misinterpreted the results of his analysis, and that when this error is corrected the results of the Acoustic Analogy are brought into exact agreement with the well-known Rankine–Hugoniot solution of the Euler equations.

Fan Casing Noise Radiation

1991 ◽  
Vol 113 (1) ◽  
pp. 37-42 ◽  
Author(s):  
G. H. Koopmann ◽  
W. Neise ◽  
K. A. Cunefare
Keyword(s):  
Sound Pressure ◽  
Noise Spectrum ◽  
Centrifugal Fan ◽  
Noise Sources ◽  
Fan Noise ◽  
Noise Radiation ◽  
Starting Point ◽  
Element Program ◽  
Inlet Box ◽  
Subharmonic Frequency

This paper presents a method for assessing the extent of casing noise radiation of a centrifugal fan relative to the aeroacoustic sources associated with the inlet box of the fan. Central to the method is a boundary element program which is used to compute the acoustic pressures on the surfaces of the fan casing in terms of its surface vibration which in this case was measured experimentally. Data from an earlier experiment was used as the starting point for this study. Available data included sound pressure measurements near and away from the inlet box of the fan and vibration measurements over the casing of the fan. Noise from the outlet duct of the fan was purposely highly attenuated. Computations of sound pressure, intensity, and power indicated that, at the blade passing frequency (300 Hz), the aerodynamic sources generated near the entrance plane of the inlet box of the fan dominate the noise spectrum in the field. On the other hand, at the first subharmonic frequency of the blade tone (150 Hz), the sound power generated from the inlet box and fan casing are within 3 dB of each other. Thus, for effective noise control at this frequency, it would be necessary to include both noise sources in the overall treatment.

Turbojet Engine Noise Prediction Utilizing Empirical Methods

2013 ◽  
Author(s):  
João Roberto Barbosa ◽  
Daniel Jonas Dezan
Keyword(s):  
Gas Turbines ◽  
Sound Pressure ◽  
Noise Prediction ◽  
Octave Band ◽  
Empirical Methods ◽  
Engine Noise ◽  
Noise Sources ◽  
Turbojet Engine ◽  
Sound Pressure Levels ◽  
The One

This work deals with the prediction of noise generated by gas turbines, which includes engines being designed. One has in mind the fulfillment of the ever-increasing concerns with environment, in particular noise. Analytical and empirical methods have been focused by researchers and industry, although only empirical prediction methods are utilized in this work, for the calculation of the one-third octave band sound pressure levels associated to the main engine noise sources. The methodology for the calculation of the engine noise has been combined with performance and design computational programs to evaluate the noise emitted by each engine component and, by proper combination, the engine total noise. A newly designed and manufactured 5 kN/1.2 MW turbojet engine serves as the basis for the noise prediction. For the study, the main noise sources are: compressor, combustor, turbine and propelling nozzle. In terms of the overall sound pressure level, OASPL, are compatible with the noise produced by similar engines. The noise predictions are performed at engine design speeds in the range of 100% down to 70% of the design speed (28,150 rpm). The engine has not run yet, but it is expected that measured noise will be available in the near future. However, it is important to emphasize that all prediction models used to evaluate the radiated noise from the engine were validated. The engine operating conditions were calculated using a high fidelity engine simulator developed to provide the data used in this study. The methods to estimate the one-third octave band sound pressure levels are reported in NASA TM-195480, SAE ARP-876D, NASA-ANOPP and ESDU Item 98019. No atmospheric attenuation and ground reflection were considered in this work.

scholarly journals The role of compressibility in computing noise generated at a cavitating orifice

2018 ◽  
Vol 18 (1) ◽  
pp. 73-91 ◽  
Author(s):  
Amir Bashirzadeh Tabrizi ◽  
Binxin Wu
Keyword(s):  
Mach Number ◽  
Flow Field ◽  
Sound Pressure ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Physical Situation ◽  
Low Frequencies ◽  
Sound Pressure Levels ◽  
Dynamics Calculation

The computational fluid dynamics calculation can be accomplished by solving either compressible or incompressible Navier–Stokes equations to determine the flow-field variables of the noise source. The proper assumption depends on both the physical situation and the Mach number. Although in cavitating devices usually we are dealing with low Mach number flow, cavitation is an acoustic phenomenon that can be affected by compressibility. Cavitation behaves acoustically as a monopole and it is mentioned by some researchers that incompressible solution is sufficient to study the dipole sources. However, in order to study the monopole (and quadrupole) sources a compressible solution may be required. In this study, the role of compressibility in computing noise generated at a cavitating single-hole orifice was investigated using large eddy simulation and Ffowcs Williams–Hawkings formulation. The fluid zone downstream of the orifice where the cavitation occurs was evaluated as the acoustic source which generates sound. Time-accurate solutions of the flow-field variables on source surfaces were obtained from both compressible and incompressible flow simulations. Three cases of cavitation were studied and the sound pressure signals far downstream of the orifice were computed by the Ffowcs Williams–Hawkings formulation. For a developed cavitation regime at low frequencies, there is a big discrepancy between the computed values of sound pressure level from compressible and incompressible simulations, and at higher frequencies greater than 6 kHz, both simulation methods provide almost the same values for sound pressure levels. For a super cavitation regime, both compressible and incompressible simulations provide similar values for sound pressure levels at frequencies greater than 2 kHz. The results of this work demonstrate that the compressibility has a significant role in terms of computing noise generated at a cavitating orifice and cannot be ignored, especially when the noise generated by developed cavitation regimes at low frequencies is investigated.

Construction Noise Annoyance among the Public Residents

2015 ◽  
Vol 74 (4) ◽  
Author(s):  
Nadirah Darus ◽  
Zaiton Haron ◽  
Siti Nadia Mohd Bakhori ◽  
Lim Ming Han ◽  
Zanariah Jahya ◽  
...  
Keyword(s):  
Sound Pressure ◽  
Construction Sites ◽  
Noise Sources ◽  
High Noise ◽  
The Public ◽  
Noise Annoyance ◽  
Sound Pressure Levels ◽  
Relationship Of ◽  
The Relationship

Construction activities generate construction noise may cause noise annoyance among the public residents. The aim of this study is to investigate the noise annoyance level due to the sound pressure levels and the distances from the construction sites. Three public resident areas around Johor which located near to the construction sites have been selected. Two important indicators such as sound pressure levels and distances between the receiver and the noise sources were measured. 42 questionnaires were randomly distributed to the public residents who live near to the construction sites. The results showed that all respondent have different annoyance levels due to the construction noise. The sound pressure levels received by the public residents are increasing with the decreasing of the distance between the receiver and the noise sources. Thus, the relationship of noise annoyance levels is directly proportional to the sound pressure levels produced from construction sites. Meanwhile, the noise annoyance levels are decreasing with the increasing of the distances. As a conclusion, the public residents who live nearer to the construction sites suffered from a high noise annoyance level as expected.

Comparison of noise generated from simplex and duplex configurations of drum brake using non-linear vibro-acoustic models

2021 ◽  
Vol 263 (5) ◽  
pp. 1415-1425
Author(s):  
Akash Yella ◽  
Sriram Sundar
Keyword(s):  
Degrees Of Freedom ◽  
Sound Pressure ◽  
Acoustic Analysis ◽  
Transfer Functions ◽  
Acoustic Noise ◽  
Contact Friction ◽  
Acoustic Models ◽  
Non Linear ◽  
Sound Pressure Levels ◽  
Drum Brakes

The drum brakes used on the rear wheels of automobiles have various configurations. These contribute to the differences in kinematic (geometry) and dynamic (contact, friction) aspects, eventually leading to significantly different vibration and acoustic response. This work attempts to estimate the difference in the vibro-acoustic noise generated by the drum brake's simplex and duplex variants using a combination of non-linear analytical vibration models and a numerical acoustic model. Four degrees-of-freedom lumped parameter models developed for the simplex and the duplex configurations with conformal contact predict the contact and reaction forces during braking. These forces act as the sources for the finite element based acoustic models developed for the two configurations to obtain the sound pressure to force transfer functions. The sound pressure levels are estimated by the product of the predicted forces with the respective transfer functions in the frequency domain. The sound pressure levels of the simplex and duplex drum brakes are quantitatively compared under different braking conditions, and the results are presented. It is expected that this vibro-acoustic analysis will help in designing quieter drum brakes.

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