Application of dual reciprocity boundary element method to predict acoustic attenuation characteristics of marine engine exhaust silencers

In marine engine exhaust silencing systems, the presence of exhaust gas flow influences the sound propagation inside the systems and the acoustic attenuation performance of silencers. In order to investigate the effects of three-dimensional gas flow and acoustic damping on the acoustic attenuation characteristics of marine engine exhaust silencers, a dual reciprocity boundary element method (DRBEM) was developed. The acoustic governing equation in three-dimensional potential flow was derived first, and then the DRBEM numerical procedure is given. Compared to the conventional boundary element method (CBEM), the DRBEM considers the second order terms of flow Mach number in the acoustic governing equation, so it is suitable for the cases with higher Mach number subsonic flow. For complex exhaust silencers, it is difficult to apply the single-domain boundary element method, so a substructure approach based on the dual reciprocity boundary element method is presented. The experiments for measuring transmission loss of silencers are conducted, and the experimental setup and measurements are explained. The transmission loss of a single expansion chamber silencer with extended inlet and outlet were predicted by DRBEM and compared with the measurements. The good agreements between predictions and measurements are observed, which demonstrated that the derived acoustic governing equation and the DRBEM numerical procedure in the present study are correct.

APPLICATION OF THE DUAL RECIPROCITY BOUNDARY ELEMENT METHOD TO SOLUTION OF NONLINEAR DIFFERENTIAL EQUATION

In this paper the dual reciprocity boundary element method is employed to solve nonlinear differential equation del(2) u + u + epsilon u(3) = b. Results obtained in an example have a good agreement with those by FEM and show the applicability and simplicity of dual reciprocity method (DRM) in solving nonlinear differential equations.

NUMERICAL MODELING OF TRANSIENT MAGNETO-THERMO-VISCOELASTIC WAVES IN A ROTATING NONHOMOGENEOUS ANISOTROPIC SOLID UNDER INITIAL STRESS

A numerical model based on the dual-reciprocity boundary element method(DRBEM)for studying the transient magneto-thermo-viscoelastic waves in a rotating nonhomogeneous anisotropic solid is presented.The formulation is tested through its application to the problem of an initially stressed solid placed in a constant primary magnetic field acting in the direction of the z-axis and rotating about this axis with a constant angular velocity.In the case of plane deformation,a numerical scheme for the implementation of the method is presented and the numerical computations are carried out for the temperature,displacement components and thermal stress components.The validity of DRBEM is examined by considering a magneto-thermo-viscoelastic solid occupies a rectangular region and good agreement is obtained with existent results.The results obtained are presented graphically to show the influence of initial stress on the displacement components and thermal stress components.