3D Aeroacoustics Simulation of a Complete Bus Exhaust System 2012-36-0632
Health related problems in over populated areas are a major concern and as such, there are specific legislations for noise generated by transport vehicles.
In diesel powered commercial vehicles, the source for noise are mainly related to rolling, transmission, aerodynamics and engine. Considering internal combustion engine, three factors can be highlighted as major noise source: combustion, mechanical and tailpipe. The tailpipe noise is considered as the noise radiated from the open terminations of intake and exhaust systems, caused by both pressure pulses propagating to the open ends of the duct systems, and by vortex shedding as the burst leaves the tailpipe (flow generated noise).
In order to reduce noise generated by vehicles, it is important to investigate the gas interactions and what can be improved in exhaust line design during the product development phase.
The objective of this work is to investigate the exhaust tailpipe flow induced noise using 3D-CFD based numerical simulation software and correlate with experimental tests acquired from a 4×2 front engine bus. The numerical approach applies steady-state realizable k-Omega turbulence with broadband noise source models to identify the frequency that will be resolved by the mesh and thus refine it as required. Then a transient simulation with DES-based turbulence model and a FFT analysis on pressure data to evaluate the noise level was performed.