Three-Dimensional Aeroacoustic Numerical Simulation of Flow Induced Noise of Mufflers

Abstract

Mufflers are widely applied in industrial flow duct systems or internal combustion engines, to reduce the amount of noise carried by the upstream flow. Although the flow in the duct of the muffler is commonly unsteady, complex and turbulent, which generates noise by itself. The flow noise should be considered for design and optimization of the muffler. By means of a three-dimensional numerical simulation integrated CFD (computational fluid dynamics) and CAA (computational aeroacoustics), the paper investigated two typical mufflers. The first one has an expanded chamber in the duct, and the second one has the same chamber but whilst has a perforated wall between the duct and the chamber. The nonlinear acoustic solver is implemented to model noise generation and transmission from an initial statistically-steady turbulent flow, which provided by RANS (Reynolds-averaged Navier-Stokes) simulation, and to simulate the noise in near field. The radiated far-field noise of the mufflers was predicted by FW-H (Ffowcs Williams-Hawking) acoustic analogy. The mechanisms of the vortex and sound generation were revealed, and results indicate that the perforated tube muffler has much lower flow induced noise level. The solver of the numerical simulation has been parallelized with MPI, and run on a HPC cluster, due to the large computation cost.