Bulletin of the American Physical Society
74th Annual Gaseous Electronics Conference
Volume 66, Number 7
Monday–Friday, October 4–8, 2021;
Virtual: GEC Platform
Time Zone: Central Daylight Time, USA
Session BM22: Workshop II: Plasma Modeling |
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Chair: Vladimir Kolobov, CFDRC, University of Alabama in Huntsville Room: Virtual GEC platform |
Monday, October 4, 2021 8:30AM - 9:15AM |
BM22.00001: Using commercial, academic, and open-source software for low temperature plasmas: Fluid and Hybrid methods Invited Speaker: Robert Arslanbekov We present a broad overview of commercial, academic, and open-source software for low temperature plasmas focusing on fluid and hybrid methods. Key features of of CFD-ACE [1], COMSOL [2], VizGlow [3], Usim [4], gerris/basilisk [5], and openFOAM [6] are evaluated and compared with respect to physical models and numerical techniques. The most important differences between these computational tools consist of different methods of mesh generations and discretization of PDEs describing plasma. The first class of tools uses body-fitted structured and unstructured static mesh, which can be highly non-uniform to account for large gradients of plasma parameters in the narrow space-charge sheaths. The second class uses non-surface-aligned mesh, which can be automatically generated around embedded objects and can be dynamically adapted to solution properties and moving boundaries. The second difference between the tools consist of discretizing PDEs using FV and FE methods. The third difference is how the sets of the equation are solved: in a coupled way or sequentially. In terms of physics, fluid models are typically used for ions and neutrals whereas electrons can be described by either a fluid model, by solving grid-based kinetic equations, or using particle-based methods. An external circuit simulator is often needed, which controls the time step in coupled plasma-circuit computations. When the time-stepping schemes are implicit, a nonlinear system of equations must be solved each time step (e.g., Newton solver). We will illustrate the benefits and drawbacks of different software packages on selected gas discharge problems and discuss current challenges and potential future developments. |
Monday, October 4, 2021 9:15AM - 10:00AM |
BM22.00002: Recent developments in the kinetic simulations of low-temperature plasmas Invited Speaker: Zoltan Donko Kinetic simulations have been aiding the understanding of the physics of low-temperature plasma sources for several decades. The pioneering studies required access to mainframe / supercomputers of those times, the evolution of computing hardware made these approaches widely accessible; smaller scale simulations can be executed now on desktop / laptop computers. The advance of the computing capabilities was accompanied with improvements of the accuracy and complexity of modeling. The recent developments allow increasing the number of simulation particles by orders of magnitude, suppressing noise and artificial heating effects. Also, widening of the parameter domains became possible, e.g., low pressure discharges operated at extreme conditions (very low pressures and very high voltages) and high (atmospheric) pressure discharges of plasma jets can now be described accurately. Enhancing the reliability and the predictive capability of computational modeling requires benchmarking between different codes, as well as validation of the discharge models and verification of the codes implementing these models. This calls as well for precise reference experiments for measurements of plasma characteristics. |
Monday, October 4, 2021 10:00AM - 10:15AM |
BM22.00003: Coffee Break Coffee Break |
Monday, October 4, 2021 10:15AM - 11:00AM |
BM22.00004: Grid-based kinetics solvers and AMAR technique Invited Speaker: Vladimir I Kolobov Kinetic equations describe classical transport processes in terms of particle velocity distribution functions. Direct numerical solution of the kinetic equations can be obtained by discretizing phase space (which consists of configuration and velocity spaces). However, substantial challenges exist due to the high dimensionality of phase space (3d3v) in the general case. Two methods to overcome this challenge: a) use problem symmetry to reduce the dimensionality of either configuration or velocity spaces, or b) use splitting procedure to generate a separate mesh in configuration and velocity space and solve transport in these spaces sequentially. In this presentation, we describe grid-based kinetic solvers using both of these techniques. |
Monday, October 4, 2021 11:00AM - 11:45AM |
BM22.00005: SimNet: A Neural Framework for Physics Simulations Invited Speaker: Oliver A Hennigh Simulations are pervasive in every domain of science and engineering. In comparison with the |
Monday, October 4, 2021 11:45AM - 1:30PM |
BM22.00006: Lunch Break Lunch Break |
Monday, October 4, 2021 1:30PM - 2:15PM |
BM22.00007: Incorporating Open-Source Databases in a Simplified Rigid Beam Application Invited Speaker: Nancy D Isner Detailed and well documented cross-sectional data is needed for even the simplest of plasma models. The Naval Research Laboratory (NRL) evaluated plasma chemistry (nepc) Python package provides tools for curating and combining cross-sections from common sources (e.g., LXCat, QuantemolDB), adding additional metadata that helps describe the plasma dynamics. Many of these databases are pre-defined chemistry sets which provide preliminary functionality for performing exploratory data analysis when incorporated into reduced plasma models. The combined chemistry sets are evaluated in a Python packaged, Boltzmann solver (BOLOS) that is then coupled to a Python packaged, rigid-beam model1 for an electron beam generated plasma. This work shows how to connect a database, a Boltzmann solver, and a plasma model. |
Monday, October 4, 2021 2:15PM - 3:00PM |
BM22.00008: Interaction of electrons with plasma walls Invited Speaker: Franz X Bronold The interaction of electrons with the walls of the discharge vessel is an important surface process in technological low-temperature plasmas. It affects, for instance, the operation modii of dielectric barrier discharges, Hall thrusters, and divertor plasmas in fusion devices. Little is however known quantitatively about the process because it typically occurs at energies below 50 eV which are hard to access experimentally. There are only a few attempts to measure probabilities for electron absorption, backscattering, or secondary emission in this energy range. From a theoretical point of view the description is also challenging, because it cannot be entirely based on an ensemble of individual atomic scattering centers occupying a region of space with a certain density. Instead genuine solid state effects, such as Bragg scattering on crystal planes and collective excitations of the ensemble become important. In my talk I will give a tutorial introduction into the semiempirical microscopic modeling we introduced a few years ago for calculating aforementioned probabilities [1]. It is based on an invariant embedding principle for a function Q summing up the backscattering trajectories arising from the interaction of the incoming electron with the excitations and imperfections of the wall. We substantially augmented this approach to make it applicable to metallic walls. Besides describing the augmentations, I will present for a number of metals the secondary electron emission yields we obtained from our theory. They turn out to be in good agreement with experimental data indicating that our approach captures the low-energy scattering physics rather well. |
Monday, October 4, 2021 3:00PM - 3:15PM |
BM22.00009: Coffee Break Coffee Break |
Monday, October 4, 2021 3:15PM - 4:00PM |
BM22.00010: Recent advances in modeling low-temperature kHz atmospheric pressure plasma jets and their interactions with surfaces Invited Speaker: Anne Bourdon Typically, in an atmospheric pressure plasma jet, a discharge is ignited in a noble gas (helium being the most used) flowing in a tube and the jet expands into air before impacting a target. Many studies have shown that plasma jets can generate high fluxes of reactive species at low gas temperatures. Consequently, their use has been investigated for different applications as living tissue treatment, polymer etching, water treatment and food decontamination. |
Monday, October 4, 2021 4:00PM - 4:45PM |
BM22.00011: Numerical modeling of NS discharge development in inhomogeneous magnetic field Invited Speaker: Andrey Starikovskiy Numerical characterization of nanosecond pulsed discharges has been conducted in a strong magnetic field environment. Streamer discharge development and plasma generation in pure CO2 was analyzed when magnetic field was directed along the axis of the discharge cell. Numerical simulations were based of a two-dimensional fluid model. It is shown that strong magnetic field affect dramatically on the plasma formation. The NS streamer diameter decreases significantly, plasma density increases. Calculations were carried out for different magnetic field values for fixed CO2 pressure P = 50 Torr and fixed NS pulse voltage U = 20 kV. It can be concluded that the streamer discharge sharply changes its characteristics in inhomogeneous magnetic fields and this control mechanism could be used in numerous applications. |
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