Plasma-based Control of Supersonic Nozzle Flow
The flow structure obtained when Localized Arc Filament Plasma Actuators (LAFPA) are employed to control the flow issuing from a perfectly expanded Mach 1.3 nozzle is elucidated by visualizing coherent structures obtained from Implicit Large-Eddy Simulations. The computations reproduce recent experimental observations at the Ohio State University to influence the acoustic and mixing properties of the jet. Eight actuators were placed on a collar around the periphery of the nozzle exit and selectively excited to generate various modes, including ﬁrst and second mixed (m = +/- 1 and m = +/- 2) and axisymmetric (m = 0). In this fluid dynamics video, unsteady and phase-averaged quantities are visualized to aid understanding of the vortex dynamics associated with the m = +/- 1 and m=0 modes excited at the preferred column-mode frequency (Strouhal number 0.3). The unsteady flow in both contains a broad spectrum of coherent features. For m=+/- 1, the phase-averaged ﬂow reveals the generation of successive distorted elliptic vortex rings with axes in the ﬂapping plane, but alternating on either side of the jet axis. This generates a chain of structures where each interacts with its predecessor on one side of the major plane and its successor on the other. Through self and mutual interaction, the leading segment of each loop is pinched and passes through the previous ring before rapidly breaking up, and the mean jet ﬂow takes on an elliptic shape. The m = 0 mode exhibits relatively stable roll-up events, with vortex ribs in the braid regions connecting successive large coherent structures.
Flow control; Plasma actuators; Supersonic Nozzle