Measurements of Aerodynamic Noise and Wake Flow Field in a Cooling Fan with Winglets.

The aerodynamic noise and the wake flow field in a cooling fan under actual operating conditions are studied with and without winglets on the fan blades. In order to understand the influence of the winglet, the aerodynamic noise and the wake velocity distribution are measured. The results indicated that overall noise level decreased and the noise spectrum was changed in a low frequency range when the winglet was installed. It was found from the flow visualization and PIV measurement that the influence of the winglet appeared in the traces of the tip vortices and the magnitude of vorticity was reduced in the near wake region, which suggest the observed reduction in aerodynamic noise. [ABSTRACT FROM AUTHOR]