Characterization of early stages of flow induced by spark plasma discharges using high-speed PIV and BOS*

The local flow field generated by spark plasma is important in flow control and plasma assisted combustion applications. The spark creates rapid heating of the gas and production of shock waves, resulting in an unsteady three-dimensional flow field with complex pressure and temperature gradients. The induced flow is characterized at later times by vortices that entrain ambient, cold fluid into the electrode gap where the hot gas kernel is expanding. The formation and growth of these vortices and rate of cooling of the hot gas kernel are important parameters in mixing applications, as well as the effect of the amount of energy deposited by the spark on these processes. We propose high-speed (100 kHz) simultaneous background oriented schlieren (BOS) and particle image velocimetry (PIV) measurements to quantify density gradients and coherent structures induced by the spark within the first 100 µs of the flow using a range of spark energies. These measurements will be used to investigate the mechanisms responsible for the formation of vorticity by spark plasmas and how these mechanisms are affected by variations in energy.