Computational and experimental study of the synchronization strategies of two pulsing jet fluidic oscillators

Abstract

Fluidic oscillators are interesting actuators for flow control purposes as they produce unsteady jets without any moving part. Flow separation control in a large scale, for instance on a wing, needs an array of such actuators, whose efficiency can be improved if the pulsed jets are synchronized. In this paper, two synchronization configurations based on interconnections of the feedback loops have been applied successfully to two bi-stable fluidic oscillators. The first configuration permits to obtain jets pulsating at a similar frequency as the jets produced by the oscillators working separately. The second configuration, which differs by the interconnection pattern, leads to a much lower frequency. Two different phase lags between the jets produced by the two oscillators have also been identified, depending on the interconnection pattern. These experimental results have been completed by a numerical study of the internal flow patterns of the two oscillators for an in-depth analysis of the physical mechanisms controlling the oscillation dynamics. In the first synchronization configuration, the oscillation is shown to be mainly controlled by the back and forth propagation of pressure waves in the oscillators' branches and feedback loops and its frequency can be estimated by the same simple relation as the one used for single oscillators. In the second synchronization configuration, the jet switching time is no more negligible compared to the pressure waves propagation time, leading to more complex oscillation dynamics.