Research on the directional characteristics of wind noise emitted by bionic rods

In this paper, the directional characteristics of wind noise emitted by different bionic rods were studied based on a hybrid computational aeroacoustics method. The noise reduction mechanism of surface grooves, pits, and bumps was analyzed, respectively. The basic principle of noise reduction is to reduce the influence of the vortex shedding on the rod by changing the shape of the rod or passive control technology to reduce the dipole sound source. The unsmooth transverse surface will increase the loss of flow on the leading edge of the rod and reduce the vertical effect of vortex shedding on the rod. The convex leading edge of the rod can help to transfer the vertical noise from low frequency to high frequency and reduce the vertical effect of wake vortex shedding to reduce the peak sound pressure level. The cost of those was the increase in the aerodynamic drag and the increase in noise in the flow direction (the increase in the amplitude of drag fluctuation). In particular, the longitudinal v-groove structure on the surface of the elliptical rod can reduce the circumferential aerodynamic noise while keeping the aerodynamic drag coefficient unchanged.