Quantitative study of the aerodynamic sound induced by the flow past a cylinder based on dipole and quadrupole models

Computational fluid dynamics (CFD) associated with acoustic analogy theory was employed to numerically study the aerodynamic sound induced by the flow past a cylinder in the subcritical regime. The goal is to testify the reliability and accuracy of Curle's dipole and Lighthill's quadrupole source models according to the acoustic analogy theory. The 3-D unsteady turbulent flow fields were calculated by Large Eddy Simulation (LES) method. The equivalent sources were extracted from the time history flow data with Fourier Transform applied to extract the components at the vortex shedding frequency. The sound radiation by Curle's theory was obtained by a numerical surface integral, and a good agreement with the sound measurement was found. The sound radiation of Lighthill's quadrupoles was obtained by solving the inhomogeneous Helmholtz equation, and erroneous results might arrived at if the volumetric sources were truncated inappropriately. The study indicates that Curle's model is superior to Lighthill's model based on its more reliable results and low computational cost.