Towards Three-Dimensional Optimised Schwarz Methods without Overlap for Predicting Transmission Loss in Mufflers and Silencers

2009 ◽  
pp. 219-238
Author(s):  
F. Magoulès
Keyword(s):  
Transmission Loss ◽  
Three Dimensional ◽  
Schwarz Methods

A CFD APPROACH TO THE COMPUTATION OF THE ACOUSTIC RESPONSE OF EXHAUST MUFFLERS

2005 ◽  
Vol 13 (02) ◽  
pp. 301-316 ◽  
Author(s):  
A. BROATCH ◽  
X. MARGOT ◽  
A. GIL ◽  
F. D. DENIA
Keyword(s):  
Numerical Solution ◽  
Time Domain ◽  
Cfd Simulation ◽  
Transmission Loss ◽  
Three Dimensional ◽  
Alternative Procedure ◽  
Acoustic Response ◽  
Frequency Domains ◽  
The Time Domain ◽  
Numerical Approaches

The study of the three-dimensional acoustic field inside an exhaust muffler is usually performed through the numerical solution of the linearized equations. In this paper, an alternative procedure is proposed, in which the full equations are solved in the time domain. The procedure is based on the CFD simulation of an impulsive test, so that the transmission loss may be computed and compared with measurements and other numerical approaches. Also, the details of the flow inside the muffler may be studied, both in the time and the frequency domains. The results obtained compare favorably with a conventional FEM calculation, mostly in the ability of the procedure to account for dissipative processes inside the muffler.

scholarly journals Research of Acoustically Improved Helmholtz Resonator

2021 ◽  
Vol 7 (1) ◽  
pp. 270-278
Author(s):  
J. Li ◽  
J. Shan ◽  
Z. Guo ◽  
A. Levtsev
Keyword(s):  
Transmission Loss ◽  
Three Dimensional ◽  
Helmholtz Resonator ◽  
Acoustic Characteristics ◽  
Helmholtz Resonators ◽  
Extension Tube ◽  
Section Shape ◽  
In Series ◽  
Combined Structure ◽  
The One

The three-dimensional acoustic finite element method is used to predict the transmission loss of the Helmholtz resonance muffler. The results are in good agreement with the experimental results, indicating the applicability and accuracy of the numerical method used in this paper. On the one hand, in order to reduce the resonance frequency without changing the shape of the resonator, the connecting tube is extended to the inside of the resonator, and the influence of the extension length and the cross section shape of the extension tube on the acoustic characteristics of the resonator is discussed in detail. On the other hand, in order to broaden the muffled frequency band of the traditional Helmholtz resonators, the resonators are combined in series and parallel, and the influence of the combined structure on the acoustic characteristics is discussed in detail.

Analysis of Acoustic Performance of Compound Muffler by Finite Element Method

2012 ◽  
Vol 529 ◽  
pp. 257-263
Author(s):  
Deng Hui Cai ◽  
Xin Tan Ma
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Transmission Loss ◽  
Complex Structure ◽  
Three Dimensional ◽  
Sound Field ◽  
Acoustic Vibration ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Element Method

Since the theory of one-dimensional plane wave can not accurately predict the internal sound field of the complex structure muffler. The three-dimensional finite element method is adopted to establish the acoustic model of the composite muffler based on the application of composite muffler model. Transmission loss and characteristics of internal sound field of the composite muffler's are calculated through acoustic vibration software Sysnoise. The calculation shows that the muffler under the interference of fluid flow has the higher transmission loss compared with the absence of liquidity function with an additional silencer band. The analysis method and conclusions provide a basis for the design of composite muffler.

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.

Normal Mode Analysis of Three-Dimensional Propagation Over a Small-Slope Cosine Shaped Hill

2015 ◽  
Vol 23 (03) ◽  
pp. 1550005 ◽  
Author(s):  
Megan S. Ballard ◽  
Benjamin M. Goldsberry ◽  
Marcia J. Isakson
Keyword(s):  
Parabolic Equation ◽  
Normal Mode ◽  
Hybrid Model ◽  
Mode Coupling ◽  
Transmission Loss ◽  
Normal Mode Analysis ◽  
Three Dimensional ◽  
Mode Analysis ◽  
The Hill ◽  
Horizontal Refraction

Three-dimensional propagation over an infinitely long cosine shaped hill is examined using an approximate normal mode/parabolic equation hybrid model that includes mode coupling in the out-going direction. The slope of the hill is relatively shallow, but it is significant enough to produce both mode-coupling and horizontal refraction effects. In the first part of the paper, the modeling approach is described, and the solution is compared to results obtained with a finite element method to evaluate the accuracy of the solution in light of assumptions made in formulating the model. Then the calculated transmission loss is interpreted in terms of a modal decomposition of the field, and the solution from the hybrid model is compared to adiabatic and N × 2D solutions to assess the relative importance of horizontal refraction and mode-coupling effects. An analysis using a horizontal ray trace is presented to explain differences in the modal interference pattern observed between the 3D and N × 2D solutions. The detailed discussion provides a thorough explanation of the observed 3D propagation effects and demonstrates the usefulness of the approximate normal mode/parabolic equation hybrid model as a tool to understand measured transmission loss in complex environments.

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