Scattering by a vortex of sound wave from a moving source

This study investigates the interaction between a moving monopole point source and a vortex, with a particular focus on the spatiotemporal and frequency characteristics of the sound field. High-precision numerical simulations are employed to obtain the sound field characteristics for different vortex Mach numbers and source wavelengths. As a stationary source, the vortex disrupts the symmetry of the sound field, creating stable beam structures, with the root mean square of the scattered pressure proportional to the vortex Mach number. However, when the source is in motion, the distribution of these beams evolves over time, with noticeable bending due to interference effects as the source passes through the vortex. Both the source wavelength and the vortex Mach number significantly affect the intensity of the scattered sound, with shorter wavelengths and higher Mach numbers leading to a stronger scattered field. Moreover, the time evolution of the scattered sound can be divided into three stages: short-wave, transitional, and long-wave stages, based on observed changes in frequency and directivity. Wavelet transforms are used to analyze the time–frequency characteristics of the scattered sound pressure signals at various observation points. The frequency components of the scattered pressure exhibit a distinct shift over time and display different features at various observation locations. Finally, the instantaneous scattered sound power follows a characteristic trend of increasing and then decreasing, with the peak occurring just before the source passes through the vortex.