Far-field aeroacoustic experimental study of flow around a circular cylinder at subcritical Reynolds number

To study the aeroacoustics of the flow around a circular cylinder at subcritical Reynolds number, the experimental investigation of far-field aerodynamic noise generated from flow past a circular cylinder was carried out in D5 aeroacoustic wind tunnel at Beihang University. Under variable flow conditions in the D5 test section, the signal of the sound pressure obtained from the free-field microphones at different positions in the anechoic chamber was measured. The dependence of far-field noise on free stream velocity and receiver position was acquired with the fast Fourier transform (FFT). With the qualitative and quantitative analysis of the aeroacoustic characteristics, the experimental results validate that the noise emitted from the circular cylinder is the largest in the direction vertical to the flow and decreases with the angle increasing, belonging to the characteristics of the sound radiated from a dipole sound source. The far-field aerodynamic noise generated from the cylinder is proportional to the sixth power of flow speed and inversely proportional to the twice power of the distance between the receiver and the center of the circular cylinder, confirming the domination of the dipolar noise source.