Flow Noise Level Prediction Methods of Exhaust System Tailpipe Noise

Flow noise caused by turbulent exhaust gas is one of the dominating noise sources on high performance turbo charged and naturally-aspirated engines. Due to the broad band and random character of this specific type of noise, an exact prediction based on Navier-Stokes equations is impractical to derive. Empirical approaches with varying quality levels were developed. These empirical approaches allow estimations of the flow noise from the early concept phase up to detailed design refinements and optimizations within the development.

The main influence factors on flow noise such as temperature, mass flow and muffler design are outlined. The estimation of flow noise is based on empirical data and/or linear predictions with parametric single sources. Additional estimations are also based on more accurate, but also more time consuming, Computational Fluid Dynamics (CFD) codes for 3-dimensional flow optimization. These commercial and non-commercial Computational Aided Engineering (CAE) tools for flow noise prediction are compared in terms of quality and usability.

The influence of the muffler design with respect to flow noise and overall performance is investigated by statistical analysis of empirical data.