Analysis of Aerodynamic Sound Source with Measurement of Static-Pressure Fluctuation

Abstract

The objective of this investigation is to develop a method for detecting the aerodynamic sound source in a low-Mach number turbulent wake. We therefore introduced coherent output power (COP) in terms of surface pressure and vorticity fluctuation to evaluate vorticity contribution to aerodynamic sound generation. Moreover, aerodynamic sound source was calculated by using a modified Lighthill-Curle's equation ; that is, surface pressure fluctuation was replaced by COP. It was found that the intensity of COP corresponds to the distribution of the aerodynamic sound source caused by unsteady vorticity fluctuation. It therefore more directily reflects the aerodynamic aspects of the sound source. And we measured the distribution of aerodynamic sound source in the wake of a circular cylinder with Reynolds number of 4.0×10⁴. This measurements show that aerodynamic sound is generated near the formation region of Karman vortices. It is therefore concluded that the separated shear layers play an important role in generating aerodynamic sound. Moreover, our identification method by using COP can successfully evaluate aerodynamic properties of a sound source.