Influence of mean flow on acoustic attenuation performance of straight-through perforated tube reactive silencers and resonators

The three-dimensional (3-D) time-domain CFD approach is employed to predict and analyze the acoustic attenuation performance of straight-through perforated tube reactive silencers and resonators. A pressure pulse is imposed at the inlet, and then the 3-D unsteady flow computation is performed to acquire the time histories of the pressures at the upstream and downstream of silencer. The pressures in time-domain are then transformed to the acoustic pressures in frequency-domain by using FFT to determine the transmission loss of silencer may be determined. Transmission loss predictions of straight-through perforated tube reactive silencers without and with mean flow are compared with experimental results available in the literature, and reasonable agreements are observed. The 3-D time-domain CFD approach is then used to investigate the influence of mean flow on acoustic attenuation performance of straight-through perforated tube reactive silencers and resonators. The numerical results show that mean flow decreases the transmission loss at lower frequencies somewhat and resonance peaks remarkably of straight-through perforated tube reactive silencers and resonators and increases the acoustic attenuation at higher frequencies, especially above the plane wave cut-off frequency.