Experimental investigation of the aeroacoustic phenomenon around a circular cylinder

Abstract This paper reports on an experimental investigation of the interaction between an acoustic field and the aerodynamic field generated by fluid flow around a rigid cylinder. An experimental system was designed to create an acoustic field crosswise to the flow stream and to the cylinder axis. Sensors and signal conditioners were used to measure unsteady aeroacoustic forces of low intensity. The velocity components and the degree of turbulence of the aerodynamic field in the test section were measured by using Doppler-laser anemometry. The spatial distribution of the acoutic field around the cylinder was determined by measuring the dynamic pressure created by two loudspeakers vibrating in opposite phase. The aeroacoustic phenomenon was revealed by showing that the phase of the transfer function between the acoustic field produced by the source and the acoustic field modified by the fluid flow lies within the frequency range that corresponds to vortex shedding. In steady state flow, the acoustic wave damping coefficient was evaluated by using an aeroacoustic model. The aeroacoustic coefficients were calculated for an isolated tube and for a row of tubes with a short pitch (five diameters). A systematic investigation for different acoustic amplitude fields showed that the aeroacoustic force is a linear function of the wave amplitude at low amplitudes. The resulting coefficients are compared with the aeroacoustic coefficients for an isolated tube.