IDENTIFICATION OF FLOW STRUCTURES IN A CLOSED CHAMBER IN THE PRESENCE OF A NEEDLE PLASMA ACTUATOR

This study deals with the experimental characterization of the induced flow dynamics by a disk-needle type plasma actuator driven by sinusoidal generator and located in a rectangular cross-section burner. Flow characterization was performed using different plasma actuation conditions and standoff distances. Experiments were conducted under non-reactive flow conditions. An electrical characterization was carried out. Airflow behaviour was also analyzed using smoke flow visualization. Smoke flow visualization showed the dynamic behavior of the plasma induced flow . Post-processing of high-quality images was performed by using Proper Orthogonal Decomposition (POD) technique to recognize the dominant flow vortexes and coherent structures. This could help to design the plasma actuation in real combustors as well as could be useful for the implementation of numerical models. Moreover, it has been concluded that flow dynamics can be controlled by a variation of the plasma power or of the gap distance between two electrodes. Laser Doppler Velocimetry (LDV) was used to investigate the distribution of flow velocities and turbulent kinetic energy at different plasma power values of the sinusoidal AC generator and standoff distances. From POD and LDV analyses, it has been observed that there is a quite linear relation between POD energy of the first mode and the maximum turbulent kinetic energy (TKE). The proper orthogonal decomposition (POD) method could be used to identify motions in the flow field carrying the most turbulent kinetic energy (TKE). TKE peaks are present in the area with the most energetic flow structures, as identified by the POD.