Flow Induced Aerodynamic Noise Analysis of Perforated Tube Mufflers

2012 ◽  
Vol 29 (2) ◽  
pp. 225-231 ◽  
Author(s):  
C.-N. Wang ◽  
C.-C. Tse ◽  
S.-C. Chen
Keyword(s):  
Transmission Loss ◽  
Noise Analysis ◽  
Helmholtz Resonator ◽  
Aerodynamic Noise ◽  
Mean Flow ◽  
Flow Effect ◽  
Flow Induced Noise ◽  
The Mean ◽  
Cfd Method ◽  
Perforated Tube

AbstractDespite the analysis of muffler performance for many years, most works focus mainly on reducing inlet sound and fail to consider the flow effect. Most of their results correlate well with the experimental measurements. Subsequent works have considered the mean flow effect. Owing to Doppler's effect, transmission loss curve of the muffler will shift in its corresponding frequency. However, the correlation is worse than the experimental results since the flow induced noise does not include in the analysis. This work elucidates how flow induced noise affects muffler performance by analyzing a uniform flow that passes through perforated mufflers. The flow field is calculated with the CFD method, followed by evaluation of the aerodynamic noise based on the simulation results. Additionally, the procedure is simplified by computing and comparing only the total sound power induced by the flow in the muffler interior. Two muffler types, Helmholtz resonator and plug perforated tube muffler, are analyzed and discussed.

A Green’s Function Solution for Acoustic Attenuation by a Cylindrical Chamber With Concentric Perforated Liners

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
D. Veerababu ◽  
B. Venkatesham
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Velocity Potential ◽  
Transmission Loss ◽  
Analytical Models ◽  
Mean Flow ◽  
Cylindrical Chamber ◽  
Function Solution ◽  
Grazing Flow ◽  
The Mean

Abstract In this study, a Green’s function-based semi-analytical method is presented to predict the transmission loss (TL) of a circular chamber having concentric perforated screens. Initially, the Green’s function is developed for a single-screen configuration as the summation of eigenfunctions of the inner pipe in the absence of the mean flow. The inlet and the outlet ports are modeled as oscillating piston sources. A transfer matrix is formulated from the velocity potential generated by the piston sources. The results obtained from the proposed method are validated with the numerical and analytical models and with the experimental results available in the literature. Later, the method has been extended to the double-screen configuration. The effect of the additional perforated screen on the TL is studied in terms of the surface impedance of the chamber. Along with grazing flow considerations, guidelines are provided to incorporate more concentric perforated screens into the formulation.

ACOUSTIC ATTENUATION CHARACTERISTICS OF STRAIGHT-THROUGH PERFORATED TUBE SILENCERS AND RESONATORS

2008 ◽  
Vol 16 (03) ◽  
pp. 361-379 ◽  
Author(s):  
Z. L. JI
Keyword(s):  
Performance Prediction ◽  
Transmission Loss ◽  
Three Dimensional ◽  
Geometrical Parameters ◽  
Mean Flow ◽  
Acoustic Attenuation ◽  
One Dimensional ◽  
The One ◽  
Attenuation Characteristics ◽  
Perforated Tube

The one-dimensional analytical solutions are derived and three-dimensional substructure boundary element approaches are developed to predict and analyze the acoustic attenuation characteristics of straight-through perforated tube silencers and folded resonators without mean flow, as well as to examine the effect of nonplanar waves in the silencers and resonators on the acoustic attenuation performance. Comparisons of transmission loss predictions with the experimental results for prototype straight-through perforated tube silencers demonstrated that the three-dimensional approach is needed for accurate acoustic attenuation performance prediction at higher frequencies, while the simple one-dimensional theory is sufficient at lower frequencies. The BEM is then used to investigate the effects of geometrical parameters on the acoustic attenuation characteristics of straight-through perforated tube silencers and folded resonators in detail.

A Numerical Analysis for Perforated Muffler Components with Mean Flow

1999 ◽  
Vol 121 (2) ◽  
pp. 231-236 ◽  
Author(s):  
Chao-Nan Wang
Keyword(s):  
Wave Propagation ◽  
Performance Prediction ◽  
Present Method ◽  
Mean Flow ◽  
Acoustic Performance ◽  
Higher Order Modes ◽  
Element Approach ◽  
The Mean ◽  
Perforated Tube ◽  
Plane Wave Propagation

A boundary element approach for analyzing the perforated muffler components with mean flow is developed. Most of the research on perforated mufflers is based on the assumption of plane wave propagation. In the present method, the effects of mean flow, including the convection effect in governing equation and the change of acoustic impedance of perforated tube, are considered and the influences of higher order modes are also included. The acoustic performance prediction is performed on the perforated intruding tube mufflers and also on the plug muffler with and without mean flow. Comparisons of the influences of various porosity, the mean flow velocities, the tube thickness and the hole diameters are investigated. However, the results need to be verified by further experimental measurement.

Aerodynamic Noise Assessment Using CFD/CAA Technique

2008 ◽  
Author(s):  
Slawomir Dykas ◽  
Wlodzimierz Wroblewski ◽  
Tadeusz Chmielniak
Keyword(s):  
Flow Field ◽  
Euler Equations ◽  
Aerodynamic Noise ◽  
Mean Flow ◽  
Acoustic Fluctuations ◽  
Field Assessment ◽  
Noise Assessment ◽  
Cfd Method ◽  
Wide Family

In the presented paper a numerical method for aerodynamic noise assessment on the basis of unsteady mean flow field data has been presented. This method belongs to the very wide family of so called hybrid CFD/CAA methods. In described method for calculations of the acoustic fluctuations a solution of full non-linear Euler equations is used. The Euler equations are solved with the use of numerical scheme with third order accuracy in space and time. The presented method is numerically decoupled with CFD solution, so that the information about mean unsteady flow field can be obtained using arbitrary CFD method (solver). The accuracy of the acoustic field assessment depends on the quality of the CFD solutions.

Numerical Mode Matching Approach for Acoustic Attenuation Predictions of Double-Chamber Perforated Tube Dissipative Silencers with Mean Flow

2014 ◽  
Vol 22 (02) ◽  
pp. 1450004 ◽  
Author(s):  
Z. Fang ◽  
Z. L. Ji
Keyword(s):  
High Frequency ◽  
Present Method ◽  
Transmission Loss ◽  
Mode Matching ◽  
Acoustic Behavior ◽  
Frequency Range ◽  
Mean Flow ◽  
High Frequencies ◽  
Perforated Tube ◽  
Double Chamber

The transfer matrix method (TMM) based on numerical mode matching (NMM) approach is developed to investigate the acoustic behavior of double-chamber perforated tube dissipative silencer with mean flow. The present method is verified by comparing the transmission loss (TL) predictions and experimental data. Then the effects of mean flow, perforated tube offset and lengths of perforations are studied computationally. As the Mach number increases, the TL of dissipative silencer is lowered at most frequencies. The perforated tube offset may change the acoustic behavior in the mid-high frequency range. Increasing the total length of perforations increases TL at the mid-high frequencies.

scholarly journals Aeroacoustic Attenuation Performance of a Helmholtz Resonator with a Rigid Baffle Implemented in the Presence of a Grazing Flow

2020 ◽  
Vol 2020 ◽  
pp. 1-16 ◽  
Author(s):  
Di Guan ◽  
Dan Zhao ◽  
Zhaoxin Ren
Keyword(s):  
Mach Number ◽  
Transmission Loss ◽  
Low Frequency ◽  
Helmholtz Resonator ◽  
Loss Peak ◽  
Mean Flow ◽  
Theoretical Formulation ◽  
Grazing Flow ◽  
Maximum Transmission ◽  
Rigid Baffle

To broaden its’ effective frequency range and to improve its transmission loss performance, a modified design of a Helmholtz resonator is proposed and evaluated by implementing a rigid baffle in its cavity. Comparison is then made between the proposed design and the conventional one by considering a rectangular duct with the resonator implemented in the presence of a mean grazing flow. For this, a linearized 2D Navier-Stokes model in frequency domain is developed. After validated by benchmarking with the available experimental data and our experimental measurements, the model is used to evaluate the effects of (1) the width Lp of the rigid baffle, (2) its implementation location/height Hg, (3) its implementation configurations (i.e., attached to the left sidewall or right sidewall), (4) the grazing mean flow Mu (Mach number), and (5) the neck shape on a noise damping effect. It is shown that as the rigid baffle is attached in the 2 different configurations, the resonant frequencies and the maximum transmission losses cannot be predicted by using the classical theoretical formulation ω2=c2S/VLeff, especially as the grazing Mach number Mu is greater than 0.07, i.e., Mu>0.07. In addition, there is an optimum grazing flow Mach number corresponding to the maximum transmission loss peak, as the width Lp is less than half of the cavity width Dr, i.e., Lp/Dr≤0.5. As the rigid plate width is increased to Lp/Dr=0.75, one additional transmission loss peak at approximately 400 Hz is produced. The generation of the 12 dB transmission loss peak at 400 Hz is shown to attribute to the sound and structure interaction. Finally, varying the neck shape from the conventional one to an arc one leads to the dominant resonant frequency being increased by approximately 20% and so the secondary transmission loss peak by 2-5 dB. The present work proposes and systematically studies an improved design of a Helmholtz resonator with an additional transmission loss peak at a high frequency, besides the dominant peak at a low frequency.

CFD Analysis of the Acoustic and Mean Flow Performance of Simple Expansion Chamber Mufflers

2004 ◽  
Author(s):  
J. M. Middelberg ◽  
T. J. Barber ◽  
S. S. Leong ◽  
K. P. Byrne ◽  
E. Leonardi
Keyword(s):  
Transmission Loss ◽  
Time History ◽  
Mean Flow ◽  
Inlet Pipe ◽  
Expansion Chamber ◽  
Acoustic Performance ◽  
Time Histories ◽  
History Of ◽  
Simple Expansion ◽  
The Mean

The acoustic and mean flow performance of different configurations of simple expansion chamber mufflers has been considered. The different configurations include extended inlet/outlet pipes and baffles inside the expansion section of the muffler. Both the acoustic and mean flow performance has been evaluated for each muffler. The acoustic CFD model of the muffler uses an axisymmetric grid with no mean flow and a single period sinusoid of suitable amplitude and duration imposed at the inlet boundary. The time history of the acoustic pressure and particle velocity are recorded at two points, one in the inlet pipe and the other in the outlet pipe. These time histories are Fourier transformed and the transmission loss of the muffler is calculated. The mean flow model of the muffler uses the same geometry, but has a finer mesh and has a suitable inlet velocity applied at the inlet boundary and the pressure drop across the muffler is found. The acoustic performance is compared with published experimental results.

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