Aerodynamic noise generated by two circular cylinders arranged in tandem

Abstract

The aerodynamic noise generated by two circular cylinders with different diameter ratios arranged in tandem has been investigated experimentally. In this study the diameter ratio d/D is smaller than or equal to 1, where d and D are the diameter of the upstream and downstream cylinders. Two major components were identified in the noise: one is the noise associated with vortex shedding from the cylinders (the vortex-shedding noise) and the other is the interaction noise due to the vortices impinging on the downstream cylinder. The level of the vortex-shedding noise from the upstream cylinder changes periodically if it is plotted against the spacing L, between centers of the cylinders, whereas its frequency increases asymptotically to the vortex-shedding frequency of the single cylinder in a uniform flow with increasing L. The wavelength of the periodicity was found to be associated with the distance between neighboring vortices shed from the upstream cylinder. On the other hand, the frequency of the vortex-shedding noise from the downstream cylinder is reduced by the effect of the wake of the upstream cylinder. An interaction noise was found to exist; its frequency was determined by the distance L and the free-stream velocity in the same manner as that of a self-sustained oscillating flow.