Mixing Control of a Round Jet by a Local Sound Wave

Abstract

Acoustic excitation, moving tabs, a plasma actuator and so on have been presented as methods of active control for a jet. In this study, a round jet is locally excited by a local sound wave radiated from a loudspeaker inputting a sine wave. The excited frequencies were determined with reference to the preferred frequency in the column mode of the jet. The jet was visualized using planar laser Mie scattering. Mean velocity and turbulent intensity on the jet centerline were measured using a hot wire anemometer. As a result, it is found that the acoustic excitation produces anisotropy to the spatial development of the jet, and changes of the flow structure by the frequency of the sound wave. For exciting at the preferred mode, one side of the jet expands and the other side becomes narrow. For exciting at 1/2 frequency of the preferred mode, the asymmetric structure appears in the jet.