Three-dimensional Time-domain Computation and Analysis of Acoustic Attenuation Performance of Perforated Tube Silencers

The three-dimensional time-domain computational fluid dynamics(CFD) approach is employed to compute the acoustic attenuation performance of perforated tube silencers with flow.For both cases with and without impulse signal imposed at the inlet of silencer,the time histories of the pressures at the upstream and downstream monitors of the silencer can be obtained through the unsteady calculations.The differences between two computational results at the same monitor are the impulse signal and corresponding reflective signal.The acoustic pressures in time domain are then transformed to the frequency domain by using the Fast Fourier Transform,and the transmission loss of silencer may be determined.The transmission loss of the straight-through perforated tube silencers and cross-flow perforated tube silencer is calculated using this method.The numerical predictions are compared with the experimental measurements and the calculated results from the frequency domain approach,which show that the three-dimensional time-domain CFD approach could predict accurately the acoustic attenuation performance of perforated tube silencers.Finally,the effects of gas flow velocity and temperature on the transmission loss of cross-flow perforated tube silencer are analyzed.The mean flow shifts the transmission loss curve to the lower frequency and increases the transmission loss in many frequencies.The transmission loss curve is moved to the higher frequency as the temperature increases.