76th Annual Gaseous Electronics Conference
Volume 68, Number 9
Monday–Friday, October 9–13, 2023;
Michigan League, Ann Arbor, Michigan
Session HR4: Plasma in Liquids
1:30 PM–3:30 PM,
Thursday, October 12, 2023
Room: Michigan League, Michigan
Chair: Ahmad Hamdan, Université de Montréal
Abstract: HR4.00005 : Plasma Discharge Initiation in Dissimilar Liquids
2:45 PM–3:00 PM
Abstract
Presenter:
Shuva Das
(University of South Carolina)
Authors:
Shuva Das
(University of South Carolina)
Ali Charchi Aghdam
(Univ of South Carolina)
Tanvir Farouk
(University of South Carolina)
Plasma-liquid interactions have unique properties compared to purely gas-phase chemistry. These interactions are highly non-equilibrium, extremely denser, highly reactive, and can have unique chemical selectivity. They offer ambient temperature, physical and chemical synergies at gas-liquid interfaces that enable several novel technologies. Creating a plasma strictly in the liquid phase typically requires excessively high voltages and is difficult to control. It is envisioned that liquids having dissimilar properties (e.g., drastically different permittivity) can augment the electric field strength at the interface location and promote plasma initiation. In this work, plasma discharge formation in dissimilar liquids is simulated by employing an in-house volume of fluid (VOF) mathematical modeling framework. The multi-physics model consists of Poisson’s equation solver, a species solver, and a multi-phase fluid flow solver. A VOF-based approach is used to resolve the two-phase flow problem. Properties of liquids and plasma species are updated based on the electric field and phase composition. Simulations are performed for a nanosecond pulse profile with the electrodes immersed in polar (water) and non-polar (n-heptane) liquid layers, with n-heptane being on top of the water. The inter-electrode separation distance is maintained at 1.5 mm. The evolution of interface as well as plasma dynamics as a function of the interface location from the powered electrode is investigated. It is observed that since the dielectric permittivity is discontinuous at the interface, the electric field is enhanced which depends on the relative value of the dielectric permittivity of the two liquids triggering the discharge formation at lower voltages. The highest intensity of electric forces was observed in the interface with the interface located very close to the anode tip. For the cases with interface above the tip, a higher force density is observed whereas for the cases with interface below the tip smaller force density was seen. The magnitude of electric forces has a direct relation with discharge probability in the liquid phase. Among the three electric forces, the electrostrictive ponderomotive force has the dominant effect. Simulations are conducted for single and multiple pulses with large temporal variations of the interface only observed during multiple pulses due to the slow response time of the liquid.