A time-domain finite volume approach for prediction of muffler transmission loss including thermal effects

Abstract

A time-domain finite volume approach is presented for predicting the transmission loss of muffler including thermal effects with non-uniform sound speed field and density field, in which the acoustic wave equation in heterogeneous media is solved by using unstructured finite volume method with the temperature field specified or solved by some commercial code. An improved time-domain impulse method based on the absorbing boundary condition is applied to predict the acoustic attenuation characteristics of mufflers. The approach is validated by numerical simulations of a simple expansion chamber muffler and a complex muffler with five chambers. The predicted results agree well with the corresponding experimental ones and numerical ones obtained by finite element method with commercial code SYSNOISE. The results of both mufflers under different thermal conditions indicate that the temperature distribution has a significant influence on transmission loss. According to the analysis of a complex muffler with ideal medium, it is shown that the variation of working conditions can obviously affect density and sound speed distributions but have little influence on transmission loss. On the other hand, the obtained transmission loss with the solved temperature field deviates much from the one with specified uniform temperature field.

Acoustic behaviour analysis and optimal design of a multi-chamber reactive muffler

“…The existing mature approach for studying the TL value of a reactive muffler is to use a numerical method, including the finite element method, the boundary element method and the finite volume method. Xuan et al 8 used the time-domain finite volume approach to predict the TL value of a muffler. Fang and Ji 9 used the finite element method to investigate the effects of the offset of the perforated tube, the number of perforated tubes, the hole diameter and the porosity on the transverse modes and the acoustic attenuation characteristics of circular and oval perforated-tube silencers.…”

A time-domain finite volume method for the prediction of water muffler transmission loss considering elastic walls

“…Since the structural acoustic coupling systems are solved by the time-domain FVM, the modified impulse method 12 belonging to the time-domain one is employed. p in and p tr can be obtained from their transient expressions by the fast Fourier transform (FFT).…”

“…The FEM and the BEM are much more popular than the FVM in frequency domain, due to the wide application of some commercial codes in design. Combining with the time-domain method, the finite difference method (FDM) 11 and the FVM 12 have been applied to the acoustic problems. In comparison with the frequencydomain method, the time-domain method has the following advantages: it is easy to carry out, one computation can provide the information of entire frequency band, and the computer memory requirements are not as large as those of the frequency-domain method.…”

“…The FVM is the most popular numerical method in computational fluid dynamic (CFD) problems. It has been demonstrated to be a reliable approach for the structural, [13][14][15][16] acoustic, 12 and structural acoustic 17 problems in recent years. The development of the FVM in the acoustic field is helpful for the application of a unified FVM 18 for fluid-structure-acoustic coupling problems.…”

“…Then, this method was extended to predict the TL of the air muffler including thermal effects with non-uniform sound speed and density from the commercial code Fluent. 12 Xuan et al 17 also employed this time-domain FVM to predict the transient response and natural characteristics of structural acoustic coupling systems. This article is going to further extend the application of the timedomain FVM to the acoustic problem of the water muffler with elastic walls.…”