Development and application of the dual reciprocity boundary element method for acoustic propagation in inhomogeneous axisymmetric domains

In this paper, a numerical model using the dual reciprocity boundary element method (DRBEM) is developed to model acoustic propagation in an inhomogeneous axisymmetric domain. A detailed formulation is given for the particular case of acoustic radiation from a source embedded in a region of significant temperature variation. The model is first applied to calculate the acoustic propagation within a duct in the presence of a temperature gradient along the duct central line. Results obtained show good agreement with experimental results. The model is then applied to calculate the acoustic radiation from an unflanged exhaust in the presence of temperature gradient in the vicinity of the outlet. Measured and computed transmissions losses are shown to be in close agreement. Although the formulation is presented in the context of acoustic propagation in presence of a temperature field, it applies equally well to other wave propagation problems which involve the solution of inhomogeneous, Helmholtz type equations.