Aeolian tones radiated from flow past two square cylinders in tandem

The sound generated by two square cylinders placed in a tandem arrangement in a uniform flow at low Mach numbers is studied by direct solution of the two-dimensional unsteady compressible Navier-Stokes equations. Special attention is paid to the effect of the spacing between the two cylinders on the generation mechanism of the sound. Results show that the magnitude of the generated sound varies drastically depending on the spacing. When the spacing is small, roll-up of the shear layer separated from the upstream cylinder is suppressed and the sound generation is also suppressed; near a critical value of the spacing, the magnitude of the generated sound is about 10(-2) as small as that generated by a single square cylinder. With increased spacing beyond a critical value, the shear layer separated from the upstream cylinder rolls up to form vortices in front of the downstream cylinder; the rolled-up vortices interact with the downstream cylinder, leading to a drastic increase in the magnitude of the generated sound. The results also suggest that the generated aeolian tone may show hysteresis. (C) 2006 American Institute of Physics.