"Physics Guided Simulation of Electrostatic Discharge"
by Liam Pocher

Advisor:  Prof. Daniel Lathrop

Abstract: Triboelectrically charged objects may create threshold sparks, electrostatic discharge (ESD) events, to equilibrate charge between themselves and other relatively charged objects. ESD events exhibit many complex physical phenomena.  They are a nexus of several fields of physics with disparate characteristic scales: plasma physics, chemical kinetics, hydrodynamics, circuit models, etc.  These scales can span many orders of magnitude from the varied collisions thermalizing information within a plasma on the O(fs/ps) to the physical size of the plasma channel on the O(100 μm), to the speed of a nonlinear hydrodynamic wave propagating at O(μm/ns).  These threshold ESD events may occur in situations of programmatic importance, delivering energy and power profiles to a “victim load” generating deleterious consequences. To predict and mitigate these consequences we must answer questions about the spark’s energy budget: how much energy goes into producing the spark channel; how much gets radiated away; how much energy is advected away into the hydrodynamics; and how much energy is delivered to a victim load.  An ESD simulation toolset has been created and evolved in order to answer these questions.  An appropriate, physics-guided implementation for simulation can be done by gaining insight into its constituent physics and leveraging that intuition to choose a suitable numerical operator.  We examine in detail the chemical kinetics, circuit discharge, and hydrodynamics to determine dominant regimes, values, timescales, and interactions to uncover the underlying physical dynamics.  We also examine and propose model reduction schemes for high-dimensional chemical kinetics. We use past and current work with experimentally-validated and theoretically verified hydrodynamics to calculate applicability limits of the non-ionizing strong shock limit. We quantify the energy budget from a hydrodynamic perspective and demonstrate that a significant fraction of the stored energy is “earmarked” for hydrodynamic advection as an energy terminus.  Lastly, we combine the constituent physics of an ESD event (chemical kinetics, circuit model, and hydrodynamics) into a cohesive, actionable toolset and obtain promising results from an isothermal test case.  We then propose a viable, modular evolution of the ESD toolset based upon the performed examination of the physics uncovering dominant physical scales and the stiffness of the compositional differential system.

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