Dr. Naveen Pillai
Postdoctoral Research Scholar
Department of Nuclear Engineering
North Carolina State University

Abstract

The ignition of plasmas in liquids has applications ranging from medical instrumentation to manipulation of liquid chemistry. Formation of plasmas directly in a liquid often requires prohibitively large voltages to initiate breakdown. Producing plasma streamers in bubbles submerged in a liquid having a higher permittivity can significantly lower the voltage needed to initiate a discharge by reducing the electric field required to produce breakdown.  The proximity of the bubble to electrodes and the shape of the bubbles play critical roles in the manner in which the plasma is produced in and propagates through the bubble.  Thus, a Multiphysics framework was devised to transport bubble shape data from Direct Numerical Simulation (DNS) into plasma hydrodynamics simulations wherein the plasma behavior within the bubbles could be studied.

An air/liquid plasma reactor that could reliably produce ellipsoidal bubbles was designed in which air is injected through a novel orifice geometry not unlike that of a flute submerged underwater. After validating the bubble formation behavior seen via DNS with airflow through one orifice, a much larger case was designed to simulate the evolution of bubbles produced out of many orifices in the flute, which was also validated using experiments. In the latter stages of the larger case, the physics of bubbles crashing into electrodes was resolved. The bubble shape data from this case was then transported through the novel Multiphysics framework to a plasma modeling code (nonPDPSIM) that could simulate the plasma hydrodynamics in the bubbles near the electrodes. The behavior of the plasma in those bubbles matched that seen in prior experiments, with the bulk of the plasma typically traveling on the surface of the bubbles.

The ultimate goal of this work is to set the stage for the combination of high-resolution DNS with a concurrent investigation of streamer formation within the bubbles. This will open up many new avenues of research in the field of plasma-liquid interactions and will offer unique insight into the phenomenon of plasma-induced bubble instabilities.

Biography

Naveen Pillai is currently a Postdoctoral Researcher at North Carolina State University under the direction of Dr. Igor Bolotnov. He received his Ph.D. in Nuclear Engineering in 2021, co-advised by Dr. Igor Bolotnov and Dr. Katarina Stapelmann. Prior to that, he weathered the hazards of the idiosyncrasies of the department of Chemical Engineering and Materials Science (CEMS) at the University of Minnesota to earn his Bachelor of Chemical Engineering (summa cum laude) in 2017.

His current work is focused on exploring suitable avenues for the further development of his multiphysics framework, as well as probing deeper into the chemistry and physics of plasma formation within the bubbles.

Thursday, March 3. 2022
4:00 pm seminar

Hybrid Option  (Speaker is in person)

zoom (link upon request)
or
Room 1202 Burlington Labs