Aerodynamic sound radiation of low Mach number flows around a cylinder and truncated cylinders

Taking the sound radiation of flow past cylinders as the research objective, the quantitative prediction methods of aerodynamic sound in low Mach number flows are discussed. Firstly, the intrinsic relationship between the Lighthill’s acoustic analogy and an acoustic perturbation equation based on the acoustic/viscous splitting technique, is analyzed. Secondly, based on computational fluid dynamics, the two-dimensional (2D) simulations of the subcritical flow around a cylinder and two truncated cylinders are carried out, and performances of the two turbulence models are discussed. Finally, the aerodynamic sound radiations are predicted using the FW-H equation in the Lighthill’s acoustic analogy theory as well as the non-homogeneous wave equation of the acoustic perturbation theory, and the acoustic directivity and spectral characteristics are analyzed. The numerical results show that the acoustic radiations predicted by the FW-H equation and the acoustic perturbation equation are similar in the acoustic spectra with the larger amplitude by the FW-H equation. The truncation of the cylinder at the rear part makes the wake flow fluctuations increase resulting in more intensive sound radiation.