Prediction of the Noise Reduction by Shroud Shape and the Characteristics of Flow-induced Noise Generated in an Axial Flow Fan

In this study, computational fluid dynamics (CFD) and computational aeroacoustics (CAA) were used to reduce the noise of a small axial cooling fan that is widely applied to electronic devices. The noise of an axial cooling fan that was measured in semi-anechoic room was compared with the results obtained from CAA. Three-dimensional Navier-Stokes equations were solved for the unsteady flow field simulation. The noise was calculated by using simplified Ffowcs Williams and Hawkings (FW-H) equation. The result of CAA was consistent with one data obtained from the experiment. The results of unsteady flow field presented the noise generation mechanism and that of CAA presented the sound sources. The shape of a shroud was a factor causing one of the major noise sources on the fan surface. The shape modification was made in the inlet of the shroud for noise reduction. The Overall Sound Pressure Level (OASPL) was reduced by 3.7 dB compared to that predicted for Base model.