Experimental Characterization of a Car Window Excited by Turbulent Flow Using Scanning Sound Intensity Techniques

2012 ◽  
Author(s):  
Daniel Fernandez Comesaña ◽  
Eduardo Latorre Iglesias ◽  
Malcolm Smith ◽  
Hans-Elias de Bree
Keyword(s):  
Turbulent Flow ◽  
Particle Velocity ◽  
Automotive Industry ◽  
Sound Intensity ◽  
Aerodynamic Noise ◽  
Experimental Characterization ◽  
Velocity Measurements ◽  
Radiated Sound ◽  
Radiated Sound Power

Reducing the aerodynamic noise produced by turbulent flow exciting a car window is one of the current noise control challenges in the automotive industry. Flow separation and later reattachment into a turbulent boundary layer and turbulent wake occur because of flow over the A-pillar and the wing mirror. Experiments have been carried out to represent an idealised wing mirror noise problem using flow over a half cylinder exciting a flat plate. A scanning P-U (pressure-particle velocity) probe was used to measure various aspects of the window response and sound radiation, including the energy distribution of the vibrating surface, the total radiated sound power and hence the radiation efficiency. In addition, experimental results showed that the operational deflection shapes of the car window can be visualized by using scanning particle velocity measurements, obtaining similar results as with step-by-step measurements using a roving accelerometer. The scanning sound intensity maps also proved to be helpful for detecting weaknesses of the initial experimental setup as part of the experimental optimization.

Experimental Characterization of the Influence of Auxiliary Devices on the Noise Generated by Industrial Centrifugal Fan and Correlation to the Geometrical and Fluid Dynamic Parameters

2011 ◽  
Author(s):  
M. Cadorin ◽  
M. Pinelli ◽  
E. Podeschi ◽  
F. Pompoli ◽  
A. Zanardi
Keyword(s):  
Fluid Dynamic ◽  
Aerodynamic Noise ◽  
Sound Power ◽  
Centrifugal Fan ◽  
Dynamic Parameters ◽  
Experimental Characterization ◽  
Noise Sources ◽  
Additional Noise ◽  
Centrifugal Fans

In recent years, the aerodynamic noise generated by centrifugal fans is receiving increasing attention because of strict environmental noise level restrictions and customer demands. The noise generated by fans is due to aerodynamic sources and to other several sources, such as, for instance, by the fan drive, by bearings and gearing, and, when present, by the inverter. Additional noise sources can be also due to structural resonance effects induced by periodic forces associated with the blade passing frequency or vortex shedding. Usually, these additional noise sources are dominated by aerodynamic noise generated by the fan, in particular when the intake and outlet of the fan are free. On the other side, if fan intake and outlet are ducted, the additional sources can relevantly contribute to overall sound generation. In this paper, an experimental characterization of the noise generated by industrial centrifugal fans when both inlet and outlet are ducted is presented. To do this, an experimental facility has been design and set up, and the sound power measured by means of the procedures outlined in the ISO 3746 international standard. A number of different type of centrifugal fan (straight-, forward- and backward blade) in different working conditions were tested, resulting in 133 different runs. These amount of data were then processed and a general formula for fan noise estimation obtained as a function of the geometrical and fluid dynamic parameters is derived. Moreover, specific coefficients with respect to blade geometry for the determination of the A-weighted frequency spectrum are presented. Finally, auxiliary devices or other features, such as inverter, thickness of the casing, acoustic insulation, electric motor shaft, are analyzed and some general rules to estimate their influence on sound power level quantified.

Quieting Plate Modes With Optimally Sized Point Masses: A Volume Velocity Approach

1995 ◽  
Author(s):  
Hans-Walter Wodtke ◽  
Gary H. Koopmann
Keyword(s):  
Acoustic Radiation ◽  
Sound Intensity ◽  
Structural Vibration ◽  
Acoustic Response ◽  
Radiation Problem ◽  
Volume Velocity ◽  
Intensity Measurements ◽  
Radiated Sound ◽  
The Masses ◽  
Radiated Sound Power

Abstract The radiated sound power of the second symmetric mode of a clamped square plate is minimized by attaching optimally sized point masses to the plate. The plate is driven by a point force at its center and the positions of the masses are prescribed. The structural vibration problem is solved using a simple Rayleigh-Ritz approach. Solving the acoustic radiation problem is simplified by making a low-ka-assumption, i.e., the point masses are determined so as to minimize the surface volume velocity of the plate. The predicted results are verified experimentally by means of sound intensity measurements. It is shown that a structural resonance can be deleted from the acoustic response by exploiting volume velocity cancellation. The effects involved are illustrated in detail.

Vibroacoustic Characterization of a New Hybrid Wing-Body Fuselage Concept

2012 ◽  
Author(s):  
Albert Allen ◽  
Adam Przekop
Keyword(s):  
Energy Analysis ◽  
Acoustic Radiation ◽  
Analysis Model ◽  
Energy Correlation ◽  
Model Predictions ◽  
Out Of Plane ◽  
Thin Skin ◽  
Radiated Sound ◽  
Radiated Sound Power

A lighter, more robust airframe design is required to withstand the loading inherent to next generation non–cylindrical commercial airliners. The Pultruded Rod Stitched Efficient Unitized Structure concept, a highly integrated composite design involving a stitched and co-cured substructure, has been developed to meet such requirements. While this structure has been shown to meet the demanding out-of-plane loading requirements of the flat-sided pressurized cabin design, there are concerns that the stiff co-cured details will result in relatively high acoustic radiation efficiencies at frequencies well below the thin skin acoustic coincidence frequency. To address this concern and establish a set of baseline vibroacoustic characteristics, a representative test panel was fabricated and a suite of tests were conducted that involved measurements of panel vibration and radiated sound power during point force and diffuse acoustic field excitations. Experimental results are shown and compared with Finite Element and Statistical Energy Analysis model predictions through the use of modal and energy correlation techniques among others. The behavior of the structure subject to turbulent boundary layer excitation is also numerically examined.

scholarly journals Characterization of sound scattering using near-field pressure and particle velocity measurements

2019 ◽  
Vol 146 (4) ◽  
pp. 2404-2414
Author(s):  
Antoine Richard ◽  
Daniel Fernández Comesaña ◽  
Jonas Brunskog ◽  
Cheol-Ho Jeong ◽  
Efren Fernandez-Grande
Keyword(s):  
Particle Velocity ◽  
Near Field ◽  
Velocity Measurements ◽  
Sound Scattering

Measurement of sound intensity applied to the determination of radiated sound power

1973 ◽  
Vol 53 (4) ◽  
pp. 1167-1168 ◽  
Author(s):  
J. F. Burger ◽  
G. J. J. van der Merwe ◽  
B. G. van Zyl ◽  
L. Joffe
Keyword(s):  
Sound Intensity ◽  
Sound Power ◽  
Radiated Sound ◽  
Radiated Sound Power

scholarly journals Time-dependent modeling and experimental characterization of foamed EPDM rubber

2021 ◽  
Author(s):  
Stefan Buchen ◽  
Nils Hendrik Kröger ◽  
Thomas Reppel ◽  
Kerstin Weinberg
Keyword(s):  
Automotive Industry ◽  
Material Model ◽  
Tensile Tests ◽  
Time Dependent ◽  
Experimental Characterization ◽  
Compressible Material ◽  
Epdm Rubber ◽  
Finite Element Software ◽  
Cellular Microstructure

AbstractFoamed rubber with a mixed cellular microstructure is a compressible material used for various sealing applications in the automotive industry. For technical optimization, a sufficiently precise material model is required. Here a material description for the porous elastic and viscoelastic response of low density foamed rubber is proposed and adapted to ethylene propylene diene monomer (EPDM)-based rubber. The elastic description is based on a spherical shell model which is homogenized in an analytical and also in a numerical manner. A viscoelastic contribution accounts for the time-dependence of the material’s response. The derived constitutive model is implemented in a finite element software and calibrated experimentally with multi-step relaxation tensile tests of foamed EPDM rubber.

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