Affiliations: Mitsuba Corporation, 598, No, Niisato, Kiryu, Gunma,
376-0122, Japan. E-mail: a-nashi@mitsuba.co.jp | Visualization Research Center, Niigata University,
8050 Ikarashi 2, Niigata, 950-2181, Japan | Mitsuba Corporation, 1-2681, Hirosawa, Kiryu, Gunma,
376-8555, Japan
Abstract: The purpose of this study is to understand the aerodynamic noise
source distribution around a rotating fan blade by measuring the noise signal
and velocity field around the blade. The local noise-level distribution over
the fan blade is measured by microphone arrays, and the flow field is
visualized by smoke and phase-averaged PIV measurement. The noise source
distribution is examined by cross-correlation analysis between noise signal and
velocity fluctuation. It is found that the noise source is located near the
rotating fan blade, especially around leading and trailing edges. The
separation and reattachment of flow are observed near the leading edge, and the
tip vortices and vortex shedding are found near the trailing edge. The
cross-correlation distribution of the noise signal and the radial velocity
fluctuation shows large magnitude in the correlated regions, which indicates
the noise generation by the formation of vortex structure around the blade.
