Measurement of sound source distribution around a circular cylinder in a uniform flow by combined particle image velocimetry and microphone technique

Abstract

This study examined an experimental method for locating aerodynamic sound sources from a bluff body in a stream. The sound sources are evaluated from cross-correlation analysis of the pressure fluctuations on and around the flow field and the sound pressure fluctuations. Measurements are carried out in the sound field emitted from the circular cylinder at Reynolds number Re=4×104. The pressure fluctuations around the circular cylinder are evaluated by measuring the instantaneous velocity field using particle image velocimetry combined with the pressure Poisson equation, while the sound pressure fluctuations are measured simultaneously by a microphone in the far field. The experimental results showed that sound sources were found near the flow separation on both sides of the cylinder and in the near wake. The experimental results were validated by direct measurement of the pressure fluctuations on the cylinder surface using a pressure transducer. The sound sources obtained from the cross-correlation analysis agreed well with those of the direct measurement of pressure fluctuations on the cylinder surface and those around the cylinder in previous studies.