Flow Induced noise prediction in automobile exhaust systems using Computational Fluid Dynamics (CFD)

Exhaust (tailpipe) noise is an important regulation criterion for automobiles in homologation phase. The exhaust noise must meet the target dB value set by the country where the vehicle will be sold. In a typical Internal Combustion (IC) engine, the exhaust gas is pushed from the engine cylinder at the end of exhaust stroke through the exhaust system along mufflers to tailpipe. The exhaust gas product will carry two types of noise as it reaches the tailpipe, low frequency and high frequency (flow induced) noise. The high frequency noise is generated by turbulence of the gas as it passes down the exhaust all along pipes and mufflers. Computational Fluid Dynamics (CFD) can be used to calculate the high frequency noise sources inside the pipes and muffler system at any Engine Operating Point (EOP). The high frequency noise prediction can be used to optimize the gas flow distribution and noise levels.