Advanced Computational Aero-Acoustic Simulation of Complex Automotive Exhaust Systems 2011-01-0503

In the automotive sector, the time to market has become increasingly important. Consequently, powertrain systems require specific exhaust systems solutions to meet engine performance, pollutant emissions and acoustic targets delivered in a shorten time period. In this context, exhaust system suppliers need to constantly update their development process and according to project demands, tail-pipe noise has to be managed with advanced tools and methodologies. Flow generated noise has a broad band character and depending on the product design, some tonal frequencies could appear and produce a whistling noise. In order to anticipate and solve all these sound quality problems, an innovative computational aeroacoustic methodology has been developed and validated for a large range of exhaust system products. The overall approach has the advantage of making possible an aeroacoustic analysis for complex industrial models in a realistic time framework since it relies upon fast and reliable CFD analysis and on propagation tools that capture most the meaningful physics. Besides the modularity of the approach is a key factor for real industrial application. The main purpose of this paper is to discuss an advanced technique for computational aeroacoustic simulations of exhaust systems products, combining a standard CFD method with an innovative acoustic generation and propagation approach. Results will be shown comparing numerical predictions to experimental data for isolated products, such as tail pipes and silencers, and also for an integrated complex exhaust system.