Study on Mechanism of Aerodynamic Sound Generation by Flow Visualization and Fluctuating Static Pressure Measurements

Abstract

Flow visualization, particle image velocimetry (PIV), and fluctuating static pressure measurements were carried out simultaneously in a turbulent shear flow separated from a sharp-edged fence to estimate the probable location of the sound source that is closely related to vortex motion and aerodynamic sound generation. The measurement of the fluctuating static pressure is an effective way to detect vortices from pressure drops and the sound source term of the dilatation theory proposed by Ribner, which is a double time derivative of the fluctuating static pressure. Therefore, in this study, attempts were made to find the relationship between variations in the waveforms of the fluctuating static pressure, sound source term, and vortex motions obtained from the flow visualization and PIV measurements. From the results, it was revealed that pressure drops deduced from the waveforms agreed with the visualized vortices, and the waveform of the sound source term was almost the same as that of the aerodynamic sound. The results suggest that this simultaneous measurement method is useful for determining the mechanism of aerodynamic sound generation.

Keywords

• aerodynamic sound
• vortex motion
• sound source term
• flow visualization
• fluctuating static pressure
• simultaneous measurement
• dilatation theory