Control of jet using burst modulation by coaxial type DBD plasma actuator (Changes in jet diffusion process by applied voltage and burst frequency)

Abstract

This study demonstrated jet control through the generation of an intermittently induced flow via burst-modulation from a coaxial type, axisymmetric nozzle shape DBD plasma actuator (DBD-PA). Here, a lock-in phenomenon occurred and was characterized by synchronization of the burst-frequency (frequency of burst-modulation) and the jet-generated vortex within a specific burst-frequency range, which aimed to clarify the change in the development process of the jet by the driving condition of the DBD-PA where the applied voltage and burst-frequency were varied. In the main text of this study the Reynolds number that is based on mean velocity and nozzle diameter of the jet was set at 5000. The applied voltages for DBD-PA were V_p-p = 16 kV, 14 kV, and 12 kV, while the burst-frequency was f_burst = 0.2–2.0fn ( fn: frequency of occurrence of the initial vortex of free jet is 716 Hz). Results of the control demonstration showed that the lock-in phenomenon occurred at 0.9–1.4fn for all applied voltages. In the downstream, when the driving condition was V_p-p = 14 kV and f_burst = 0.7fn, diffusion was dominant in all driving conditions due to fast collapse of the developed vortex ring. Moreover, such collapse was gradual with higher applied voltage. At the end of the burst-frequency of the lock-in phenomenon range, where the driving conditions was V_p-p = 16 kV and f_burst = 1.4fn, diffusion became more suppressed as compared to the free jet, as the vortex ring near the nozzle collapsed due to vortices pairing, and did not develop. This work emphasizes that changing the applied voltage and the burst-frequency of DBD-PA potentially promotes and suppresses the diffusion of the jet.