Direct numerical simulation of aeolian tones

Aeolian tones generated by a two-dimensional circular cylinder in a uniform flow at Re = 1, 000 are investigated by a direct numerical simulation (DNS). The unsteady, compressible Navier-Stokes equations are solved by a finite difference method over the entire field from near to far fields. Results show that sound pressure waves are generated by vortex shedding from the cylinder to its wake. The dipolar nature of the generated sound is confirmed; lift dipole dominates the sound field. It is found that both the mean pressure field and the Doppler effect play important roles in the propagation process of the sound. The DNS results are compared with the solutions obtained by the Curie's acoustic analogy. The results show that the Curie's solution well describes the generation mechanisms of the sound but cannot predict the directivity of sound propagation due to the lack of information on the mean pressure field.