Caltech Young Investigators Lecture
Shock Generated Vortex Rings Drive Entrainment and Cooling in Flow Induced by a Spark Discharge
Abstract: Spark plasma actuators provide an opportunity to reduce pollutants by promoting lean combustion in engines or provide targeted, tunable, flow control over vehicles, due to their low duty cycle, large bandwidth, and light weight. However, to design scalable, high frequency actuator arrays effectively, it is necessary to understand the flow induced by a single spark discharge.
A spark discharge, generated in quiescent air, initiates a kernel of gas at high temperature (> 1000 K) and pressure (> 130 kPa) which then expands outward, producing a shock wave that lasts on the order of a few microseconds. The induced flow field following the shock wave is complex, transient, and requires diagnostics with high spatiotemporal resolution.
In this talk, I will discuss our combined theoretical and experimental characterization of the spark induced flow through a series of high spatiotemporal resolution measurements of the density and velocity fields using stereoscopic particle image velocimetry (SPIV) and background oriented schlieren (BOS) respectively, and reduced-order modeling. I will discuss our findings showing a pair of vortex rings induced near the electrode tips, as well as the role that the shock wave induced at early times plays in the generation of the vortex rings. Using the reduced order vortex ring models, we show that these rings entrain ambient gas into the hot gas kernel and control its cooling.
Bio: Bhavini Singh is a Ph.D. candidate in the School of Aeronautics and Astronautics at Purdue University, working with Prof. Sally Bane. She received her M.S. and B.S. degrees in Aeronautical Engineering from Purdue as well. Her Doctoral research focuses on characterizing the flow field induced by a single plasma discharge using high spatiotemporal resolution particle image velocimetry and background oriented schlieren measurements.
This talk is part of the Caltech Young Investigators Lecture Series, sponsored by the Division of Engineering and Applied Science.