Numerical prediction of noise from the internal flow in a centrifugal blower

The noise generated from the internal flow in a centrifugal blower was computed by computational aero-acoustics (CAA). The sound sources were obtained by computational fluid dynamics (CFD), using large-eddy simulation (LES) to compute the turbulent flow in the centrifugal blower. The computed sound pressure level (SPL) with sound source from coarse mesh LES is overpredicted, while the computed SPL with sound source from fine mesh LES agrees fairly well with the experimental data. The peak of SPL at blade passing frequency (BPF) of 600 Hz can be somewhat captured by CAA with sound source from fine mesh CFD. However, due to the short computational time, the frequency resolution is not fine in CAA with sound source from fine mesh CFD, which may be the reason of underprediction of the peak value at BPF. Fluid forces acting on the impeller at the plane perpendicular to the axial direction play important role on the predicted SPL at BPF.