The Effect of Electro-Hydrodynamics on Induced Liquid Flows During Plasma Impingement

Atmospheric non-thermal plasmas have received much attention due to their unique properties of ion and reactive species generation and delivery within “standard every day“ conditions. Applications of these plasmas can be found in a wide range of fields such as medicine, agriculture and water treatment amongst many others. One factor which has recently gaining further interest is that of the induced flow during Atmospheric Pressure Plasma Jet (APPJ) liquid target impingement. Due to the presence of a liquid phase within many APPJ applications, and the governance of flow on ion and reactive species transmission, furthering the much lacking understanding of fluid mechanics within this phase is important in potentially finding new improvements (in e.g. the species transmission flux efficiency) of atmospheric plasma applications.

The effect of grounding an APPJ liquid target on the induced liquid flow is described. The addition of the ground electrode within the solution allows current to pass through the solution and induce electrolysis on the system. A helium APPJ is impinged upon a water target for varying plasma applied voltage and solution salinity, and PIV results are compared for when this ground electrode is both absent from or submerged within the solution during these parameter investigations. The flow modifications observed included demineralised water targets having an upwards flow velocity increase with grounding, whereas in saline solutions the velocity instead increased downwards. This is believed to be due to the electrolysis exerting a net drag force on the flow, with the direction depending on the mobility coefficients of the ions present.