Suppression of Vortex Shedding from a Circular Cylinder by Internal Acoustic Excitation

Abstract

This paper reports on an experiment on the suppression of vortex shedding from a circular cylinder by internal acoustic excitation. The experiment was performed in a wind tunnel, the Reynolds numbers were in a range from 4000 to 8000, and the pure-tone sound at the natural vortex-shedding frequencies was introduced into the flow through a thin slit on the cylinder surface. It was found that vortex shedding can be suppressed by the excitation at appropriate sound levels; for a given flow condition there is an optimal sound level for the maximum suppression of the vortex shedding. This optimal excitation level is generally very weak (<80 Db), compared with the reported values which must be greater than 120 Db in order to have significant influence on wakes. The results also show that for a given Reynolds number, only in a very narrow excitation range in which the optimal sound level is located, is the vortex-shedding peak significantly reduced. Out of this range the excitation will not be able to reduce the vortex shedding.