Beat of sound generated by flow past three side-by-side square cylinders

The sound generated by three square cylinders placed in a side-by-side 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 three cylinders on the generation mechanism of the sound. Results show that, as in the case of two side-by-side cylinders, sound pressure fields as well as flow fields show different features depending on the spacing; five different patterns (weakly interactive, symmetric biased, in-phase synchronized, flip-flopping, and single bluff-body patterns) are observed in this study. In the case of three cylinders, in contrast to the case of two cylinders, a beat of sound is observed when the spacing is relatively large and thus flow interference among the three cylinders is weak.