Acoustic scattering modulation by the unsteady wake vortices in the flow around a cylinder

The acoustic scattering modulation by the unsteady wake vortices in the flow around a cylinder is numerically simulated, and the theoretical discussion on modulation mechanism is conducted from a mathematical perspective. The numerical study process is divided into three steps. Carrying out numerical simulation of the unsteady flow field around the cylinder at sub-critical region based on the CFD method. Transferring the unsteady flow data into the acoustic model through spatial and temporal linear interpolation. Solving the wave equation in fluids with unsteady inhomogeneous flow based on the discontinuous Galerkin method, the acoustic scattering modulation by the unsteady wake vortices is numerically simulated. The results show that the scattering of acoustic waves by the unsteady vortices can induce temporal modulation effect. The modulation effect indicates that discrete sidebands containing the fundamental and harmonics of the vortex shedding frequency appear on both sides of the incident acoustic frequency. The acoustic scattering modulation arises from the spatial scattering of acoustic waves by the wake vortices, as well as the periodic shedding of vortices leads to a periodic variation in the spatial distribution of the scattered acoustic field. The modulation intensity decreases linearly with the acoustic wave frequency and Reynolds number.