Chuan-Cheung Tse

A boundary element analysis of a concentric-tube resonator

Abstract A method for modeling the acoustic system of a perforated component based upon the boundary element analysis is presented. It applies to systems with complex shaped boundaries, and is not confined to the configuration which has one acoustically long dimension assumed from the traditional one-dimensional analyses. The technique can also apply to either a short or long resonator with a fully or partially perforated center tube, and has been proved by experimental measurement. The influence of mean flow, without including the convective effect, is also investigated by using the flow-induced perforated parameter.

Analysis of three dimensional muffler with boundary element method

Abstract A numerical scheme for solving the three dimensional interior acoustic problem governed by the Helmholtz equation has been developed. The main feature of this formulation is that the singularity can be removed analytically. The boundary integral equation is solved for a specific geometry by using second-order quadrilateral surface elements and does not have the difficulty of non-uniqueness associated with the boundary integral equation formulation in an exterior problem. The transmission loss of a muffler is computed by using the derived four-pole parameters. The effects of higher-order modes due to the area discontinuity as well as the various inlet/outlet alignment on the acoustic performance of a muffler are also studied. The case of a muffler with elliptic cross-section, which is troublesome in analytical solution, can be treated easily by the present scheme. Finally, the transmission loss characteristics of a muffler with extended inlet/outlet are investigated. All the numerical results are compared with experimental measurement and agreement is good.

Modeling and applications of partially perforated intruding tube mufflers

Abstract In this study, a new approach is presented for modeling concentric partially perforated intruding tube mufflers. For acoustic impedance in the linear regime, a closed form solution of the partially perforated intruding tube muffler transmission loss was first obtained. With this restriction and in the case of zero mean flow, excellent agreement between predicted and experimental results for various muffler configurations demonstrates the utility and potential of the modeling approach used in the present study. By tuning the lengths and associated physical parameters to the in-situ case of various straight-through tubular elements, one can achieve rapid and economical modeling of those that are frequently used in many commercial reactive mufflers. This modeling ability is very useful to a muffler designer especially in the preliminary design stage.

An algebraic approach for the modal analysis of synthesised structures

Abstract Based on a general eigenvalue restriction approach, a dynamic stiffness formulation of the substructure synthesis method is investigated. The modal parameters determined by this method are exact and the order of the solution matrix is equal to the number of connected co-ordinates which in many cases will be small. A superlinearly convergent scheme proposed in this paper, enables all modal parameters across a prescribed frequency range to be determined. Two examples are presented to show the computational efficiency and the validity of this method.

The scattering of an acoustic wave incident on the rigid floating body

Abstract In the present study, the sound scattering of acoustic waves incident on a rigid floating body is analyzed by the boundary element method. In the first instance, a plane wave incident on a finite cylinder and spherical body are considered. To simulate the noise produced by a propeller, a spherical incident wave generated by a point source located just behind the rigid floating body is used in the analysis. Furthermore, a sound wave incident on a floating body at different depths is also investigated.

On analysis of passive underwater acoustic damping materials

Abstract A theoretical approach has been developed to evaluate the noise reduction characteristics of underwater acoustic damping materials. In this study, materials proposed in the literature are considered and analyzed. The analysis model is based on the elastic theory and the transfer function method. The numerical result of a filled rubber materials system is verified using an experimental measurement from the literature for high frequency range (∼7 MHz). However, material suitable for a lower frequency range (∼ 20 kHz) is desired in this study. So acoustic reflective properties of materials consisting of different components are analyzed and discussed.

Effect of inner wall radius on sound attenuation in straight annular ducts

Abstract In this paper, the sound attenuation of the flow field in straight annular ducts with an assumed temperature and mean-flow distribution is investigated. The eigenvalues are solved by an IMSL package which is proposed for finding a suitable initial guess; the solution is decided iteratively. The results are shown to have high accuracy by comparison with published data. The analysis shows that the duct with the smaller inner wall radius causes more attenuation in the fundamental mode with and without spinning; however, the converse effect occurs in the lowest radial mode. There exists a great change in the resultant attenuation, when the ratio (inner wall radius to distance between inner and outer walls) is less than 1·5, and the resultant attenuation decreases for an increasing temperature or velocity gradient.