Search Results

Maximizing the acoustic attenuation is one of the important design criteria of automotive exhaust systems. Although both analytical and numerical approaches exist to evaluate the acoustic transmission properties of exhaust systems, they are, at present, insufficient to model the full geometrical complexity and to accurately assess the influence of thermal and aerodynamic phenomena onto the acoustic attenuation characteristics. For this reason, an experimental test campaign is often still indispensable to evaluate the aeroacoustic performance of exhaust systems. One of the most commonly used experimental characterization techniques for flow duct systems is the two-port characterization.

One dimensional linear acoustics network models are commonly used for the acoustic design of intake and exhaust systems. These models are advantageous since they allow the characterization of the scattering matrices for individual elements, independent of the upstream or downstream components. For an intake or exhaust assembly, the individual elements can be combined by a simple multiplication of the individual matrices to assess the propagation characteristics of the whole system under consideration. The determination of the scattering matrix coefficients can be carried out in an analytical, numerical or experimental way. Since the analytical methodologies are limited to uniform or simplified mean flow representation and the experimental two-port determination is expensive and time-consuming, a numerical method using the time domain Linearized Euler Equations is proposed in this paper.