Papers by Vladimir Kolobov
Bulletin of the American Physical Society, Oct 5, 2021
The rapid development of nanotechnology has created significant interest to predicting the behavi... more The rapid development of nanotechnology has created significant interest to predicting the behavior of materials from the atomic to the engineering scales. However, it was found that such a prediction is a very challenging problem because existing atomistic models are rather slow, while reactor-scale codes are not capable of capturing nanoscale effects. This paper addresses this problem by introducing a Multi Scale Computational Framework which couples a continuum model of reactor-scale processes, a Kinetic Monte Carlo (KMC) solver for the growth of molecular structures, and a Molecular Dynamics (MD) software for the self-assembly of atoms into molecular structures. Reactor-scale and atomistic KMC simulations were linked using a “Gap-tooth” algorithm, and KMC and MD were coupled by a “Coarse time-stepper” method.
Bulletin of the American Physical Society, 2010
Barrier Discharges (or DBDs) are used in a variety of applications from ozone generation to plasm... more Barrier Discharges (or DBDs) are used in a variety of applications from ozone generation to plasma display panels to materials processing. DBDs occur in various forms depending on conditions such as pressure, gap length, applied voltage, frequency and gas composition. In some cases, the discharge is homogenous while in other cases it may consist of several filaments. With the latter kind, a seemingly self-organized pattern of filaments is observed in several instances. In this work, we use a 3D hydrodynamic model to investigate pattern formation in dielectric barrier discharges generated in Helium. An experimental setup similar to [1] is modeled with parallel glass plates connected to plane exterior electrodes, one of which is powered. The model addresses Poisson's equation for electric potential in the domain, multispecies charge transport equations in the discharge and the surface charge balance on dielectrics. Results from these simulations including the effect of varying discharge conditions (such as pressure, gap length, voltage and dielectric properties) on the generated patterns will be discussed.
Journal of The Royal Society Interface, 2019
Reactive oxygen and nitrogen species (RONS) can influence plant signalling, physiology and develo... more Reactive oxygen and nitrogen species (RONS) can influence plant signalling, physiology and development. We have previously observed that an argon plasma jet in atmospheric air can activate plant movements and morphing structures in the Venus flytrap and Mimosa pudica similar to stimulation of their mechanosensors in vivo. In this paper, we found that the Venus flytrap can be activated by plasma jets without direct contact of plasma with the lobe, midrib or cilia. The observed effects are attributed to RONS, which are generated by argon and helium plasma jets in atmospheric air. We also found that application of H 2 O 2 or HNO 3 aqueous solutions to the midrib induces propagation of action potentials and trap closing similar to plasma effects. Control experiments showed that UV light or neutral gas flow did not induce morphing or closing of the trap. The trap closing by plasma is thus likely to be associated with the production of hydrogen peroxide by the cold plasma jet in air. Unde...
TechConnect Briefs, May 8, 2005
The rapid development of nanotechnology has created significant interest to predicting the behavi... more The rapid development of nanotechnology has created significant interest to predicting the behavior of materials from the atomic to the engineering scales. However, it was found that such a prediction is a very challenging problem because existing atomistic models are rather slow, while reactor-scale codes are not capable of capturing nanoscale effects. This paper addresses this problem by introducing a Multi Scale Computational Framework which couples a continuum model of reactor-scale processes, a Kinetic Monte Carlo (KMC) solver for the growth of molecular structures, and a Molecular Dynamics (MD) software for the self-assembly of atoms into molecular structures. Reactor-scale and atomistic KMC simulations were linked using a "Gap-tooth" algorithm, and KMC and MD were coupled by a "Coarse time-stepper" method.
Journal of Spacecraft and Rockets, Jul 1, 2008
ABSTRACT
Microelectronic Engineering, Sep 1, 2003
A kinetic module has been developed in the commercial software package CFD-ACE1 and applied to si... more A kinetic module has been developed in the commercial software package CFD-ACE1 and applied to simulations of plasma reactors for microelectronics applications. The kinetic module solves the Boltzmann transport equation (BTE) using two-term spherical harmonics expansion (SHE) of the probability distribution function (PDF). This method reduces the 6D BTE to a Fokker Planck equation in a four-dimensional space (three spatial coordinates1energy) offering a very good compromise between physical accuracy and numerical efficiency. This paper describes the design of the kinetic module and its current status and applications to electron kinetics in gas discharges. The kinetic module is coupled to other modules in CFD-ACE1 for self-consistent kinetic simulations of plasmas. The Fokker-Planck equation is solved for the electron energy probability function (EEPF) providing macroscopic characteristics (electron density, fluxes, rates of electron induced chemical reactions, etc.). Using these quantities, the transport of ions and neutrals in plasmas is simulated using a continuum model. The electromagnetic fields are calculated by solving Maxwell equations in the potential formulation (scalar electric and vector magnetic potentials). Several examples of hybrid kinetic simulations of plasma reactors are described including inductively coupled plasma (ICP), and classical DC glow discharges in electropositive and electronegative gases. The developed Boltzmann solver expands the applicability of computational plasma models to low gas pressures and enhances accuracy and fidelity of plasma simulations.
Physics of Plasmas, Jun 1, 2019
The influence of the voltage rise time on the Paschen curves is analyzed using kinetic and fluid ... more The influence of the voltage rise time on the Paschen curves is analyzed using kinetic and fluid models. The Paschen curves, which describe the dependence of the breakdown voltage, , on the product pd of gas pressure p and the characteristic length d between the electrodes, have minima that correspond to optimal conditions for plasma generation. It is shown that both kinetic and fluid models predict the experimentally observed shift of the curves toward higher voltages and the shift of the Paschen minima toward higher values of pd with decreasing the voltage rise time. On the right branch of the Paschen curves, the agreement between both models is obtained for all. We confirm that the minimum of the Paschen curves corresponds to conditions of electron runaway. At the left branch, the electron velocity distribution function is non-local in space and also non-local in time.
Bulletin of the American Physical Society, Oct 4, 2021
Bulletin of the American Physical Society, Nov 1, 2019
Bulletin of the American Physical Society, Oct 29, 2019
Submitted for the GEC19 Meeting of The American Physical Society Paschen Curves for Pulsed Breakd... more Submitted for the GEC19 Meeting of The American Physical Society Paschen Curves for Pulsed Breakdown 1 DMITRY LEVKO, ROBERT ARSLANBEKOV, VLADIMIR KOLOBOV, CFD Research-The influence of the voltage rise time on the Paschen curves is analyzed using kinetic and fluid models. The Paschen curves, which describe the dependence of the breakdown voltage, U br , on the product pd of gas pressure pand the characteristic length dbetween the electrodes, have minima that correspond to optimal conditions for plasma generation. It is shown that both kinetic and fluid models predict the experimentally observed shift of the curves toward higher voltages and the shift of the Paschen minima toward higher values of pd with decreasing the voltage rise time τ. On the right branch of the Paschen curves, the agreement between both models is obtained for all τ. We confirm that the minimum of the Paschen curves corresponds to conditions of electron runaway. At the left branch, the electron velocity distribution function is non-local in space and also non-local in time.
Journal of Applied Physics, Jan 22, 2020
This paper was selected as Featured ARTICLES YOU MAY BE INTERESTED IN Doping induced charge densi... more This paper was selected as Featured ARTICLES YOU MAY BE INTERESTED IN Doping induced charge density wave in monolayer TiS 2 and phonon-mediated superconductivity
IEEE Transactions on Plasma Science, Jun 1, 2006
We review the state-of-the-art for the simulation of electron kinetics in gas discharges based on... more We review the state-of-the-art for the simulation of electron kinetics in gas discharges based on the numerical solution of the Boltzmann equation. The reduction of the 6D Boltzmann equation to a 4D Fokker-Planck equation using twoterm spherical harmonics expansion enables efficient and accurate simulation of the electron distribution function in collisional gas discharge plasmas. We illustrate this approach in application to inductively coupled plasmas, capacitively coupled plasmas, and direct current glow discharges. The incorporation of the magnetic field effect into this model is outlined. We also describe recent efforts towards simulating collisionless effect in gas discharge plasma based on Vlasov solvers and outline our views on future development of the numerical models for gas discharge simulations.
Summary form only given. Cathode erosion is required for operation of cathodic arcs maintained by... more Summary form only given. Cathode erosion is required for operation of cathodic arcs maintained by explosive electron emission at cold cathodes.1 On the other hand, electrode erosion is an undesirable process limiting the life time of electrodes. Thus, it is desirable to uniformly distribute the arc root motion over the electrode surface to maximize its life time.
Journal of Physics D, Nov 20, 2003
The transition from Townsend to glow discharge is studied via two-dimensional simulations of disc... more The transition from Townsend to glow discharge is studied via two-dimensional simulations of discharges with moderate pd values corresponding to the right branch of the Paschen curve (p is the gas pressure and d the electrode spacing). The discharge model is coupled to the external circuit model enabling simulations of subnormal oscillations during the discharge transition from the Townsend to
2016 IEEE International Conference on Plasma Science (ICOPS), 2016
Summary form only given. Accurate simulations of high-pressure moving arcs are required for impro... more Summary form only given. Accurate simulations of high-pressure moving arcs are required for improving arc heater facilities.1 We have developed a new tool for arc simulations with Adaptive Mesh Refinement (AMR) and Volume-of-Fluid (VoF) model for electrode phenomena. It has been validated against available experimental and simulation data for several types of arcs (at gas pressures from 1 to up to 100 atm) with external DC and AC magnetic fields under LTE conditions. Good agreement has been found with available data for gas temperature, voltage drop, plasma jet velocities, Maecker jet pinch pressures, etc.2 This paper will present some of the results and discuss our development plans.
2016 IEEE International Conference on Plasma Science (ICOPS), 2016
Summary form only given. Electrode erosion in a high power arc is a limiting factor in developing... more Summary form only given. Electrode erosion in a high power arc is a limiting factor in developing more powerful gas heaters, plasma sprayers and other high current arc systems. The standard method of decreasing electrode erosion is to force the arc attachment to move in the azimuthal direction. This is done either by imposing an axial magnetic field or by rotating gas flow. Another method is suggested for further spreading the electrode heat load and thus to further reduce erosion. One or a few current carrying cables are located along the axis outside the concentric arc electrodes. These cables produce a tangential magnetic field in the inter-electrode gap, which has different directions at different azimuthal angles. Interaction of this field with the radial arc current causes the arc column to oscillate and slowly drift in the axial direction thus spreading the thermal and erosion load of the electrodes.
Bulletin of the American Physical Society, 2018
Journal of the Royal Society Interface, 2019
Plasma-generated reactive oxygen and nitrogen species can lead to closure, locking and constricti... more Plasma-generated reactive oxygen and nitrogen species can lead to closure, locking and constriction of the Dionaea muscipula Ellis trap.
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Papers by Vladimir Kolobov