Model Of Plasma Flow Research Articles

Influence analysis of uncertainty of chemical reaction rate under different reentry heights on the plasma sheath and terahertz transmission characteristics

Plasma sheath prediction of hypersonic vehicle is critical to radio frequency (RF) blackout solutions as well as vehicle design and development. In this paper, an optimized chemical reaction (OCR) model by considering the difference in reaction rate coefficient under different re-entry heights is proposed to obtain more accurate plasma sheath distribution. In the OCR model, the correction coefficient of chemical reaction rate at different heights is obtained by deriving the relationship between vehicle surface temperature and reaction rate. Further, through the coupling with hypersonic plasma flow model and co-simulation with terahertz transmission model, the influence of reaction rate uncertainty on the plasma sheath and terahertz transmission characteristics under different heights is studied. The reaction rate uncertainty has little effect on the collision frequency and sheath thickness, but has a significant effect on the electron density. Numerical simulations and comparisons with flight data validate the electron density prediction accuracy of OCR model was improved by more than 13.1% compared with the traditional chemical reaction (TCR) model, which causes prediction accuracy of signal attenuation at 0.05 THz improves about 25%, and it gradually decreases with the increasing terahertz frequency. The above conclusions are of great significance for the communication attenuation prediction and RF blackout schemes.

Difference analysis in terahertz wave propagation in thermochemical nonequilibrium plasma sheath under different hypersonic vehicle shapes

Research on terahertz communication under different vehicles has important guiding significance for the design of future hypersonic vehicle and Radio Frequency (RF) blackout. In this paper, a joint simulation model of plasma flow under thermochemical nonequilibrium state and terahertz transmission is developed to investigate the differences in terahertz wave transmission characteristics under different vehicle shapes and the related mechanisms. By comparing the plasma sheath characteristics and terahertz transmission among HIFIRE-5b (Hypersonic International Flight Research Experimentation-5b), RAM C(Radio Attenuation Measurement C) and ARD (Atmospheric Reentry Demonstrator) vehicles, it is found that the sheath thickness and electron density of ARD vehicles is significantly larger than that of HIFIRE-5b and RAM C vehicles, resulting in greater terahertz wave attenuation. Collision absorption plays a major role in the terahertz attenuation of vehicles, and the contribution of reflection effects is only observed in the ARD vehicle due to its larger plasma sheath thickness and spatial structure variation. Based on the above comparison results, a shape design scheme of reducing the vehicle head and tail for mitigating RF blackout is proposed, and the scheme is proved by further analyzing the effects of different vehicle heads and tails on the terahertz communication. With the decrease of the head radius and tail width of hypersonic vehicle, the wave attenuation at the same terahertz frequency decreases, and the contribution of reflection effect to wave attenuation gradually disappears. Therefore, the shape design scheme of reducing the vehicle head and tail can effectively alleviate the RF blackout problem, which provides an important reference value for future hypersonic vehicle design.

Three-dimensional unsteady model of arc heater plasma flow

Arc jets are unique facilities used to evaluate the performance of Thermal Protection Systems (TPS) for hypersonic vehicles. They produce high pressure and high enthalpy plasma flow to simulate the extreme heat encountered during atmospheric entry. The constricted arc heater part of an arc jet increases the test gas temperature by Joule heating. This study details the development of the three-dimensional unsteady plasma flow analysis tool, ARCHeS (ARC Heater Simulator). Coupled Navier-Stokes, radiative transfer and Maxwell equations yield current density, magnetism, radiation, and flow field solutions. The present work constitutes the first demonstration of an unsteady three-dimensional plasma flow simulation of high pressure and high enthalpy arc heater that captures kink instabilities of the electric arc. It is found that the arc attachment is mainly driven by upstream arc instabilities.

Impurity leakage and radiative cooling in the first nitrogen and neon seeding study in the closed DIII-D SAS configuration

A comparative study of nitrogen versus neon has been carried out to analyze the impact of the two radiative species on power dissipation, SOL impurity distribution, divertor and pedestal characteristics. The experimental results show that N remains compressed in the divertor, thereby providing high radiative losses without affecting the pedestal profiles and displacing carbon as dominant radiator. Neon, instead, radiates more upstream than N thus reducing the power flux through the separatrix leading to a reduced ELM frequency and compression in the divertor. A significant amount of neon is measured in the plasma core leading to a steeper density gradient. The different behavior between the two impurities is confirmed by SOLPS-ITER modeling which for the first time at DIII-D includes multiple impurity species and a treatment of full drifts, currents and neutral–neutral collisions. The impurity transport in the SOL is studied in terms of the parallel momentum balance showing that N is mostly retained in the divertor whereas Ne leaks out consistent with its higher ionization potential and longer mean free path. This is also in agreement with the enrichment factor calculations which indicate lower divertor enrichment for neon. The strong ionization source characterizing the SAS divertor causes a reversal of the main ions and impurity flows. The flow reversal together with plasma drifts and the effect of the thermal force contribute significantly in the shift of the impurity stagnation point affecting impurity leakage. This work provides a demonstration of the impurity leakage mechanism in a closed divertor structure and the consequent impact on pedestal. Since carbon is an intrinsic radiator at DIII-D, in this paper we have also demonstrated the different role of carbon in the N vs Ne seeded cases both in the experiments and in the numerical modeling. Carbon contributes more when neon seeding is injected compared to when nitrogen is used. Finally, the results highlight the importance of accompanying experimental studies with numerical modeling of plasma flows, drifts and ionization profile to determine the details of the SOL impurity transport as the latter may vary with changes in divertor regime and geometry. In the cases presented here, plasma drifts and flow reversal caused by high level of closure in the slot upper divertor at DIII-D play an important role in the underlined mechanism.

Effect of non-ionizing reaction rate (assumed to be controllable) on the plasma generation mechanism and communication around RAMC vehicle during atmospheric reentry

Radio frequency (RF) blackout occurs during radio attenuation measurement C (RAMC) vehicle reentry due to the attenuation effect of the plasma sheath on the communication signal. In recent years, the mitigation mechanism of chemical reaction for RF blackout problem has gradually been studied numerically and experimentally. However, the effect of non-ionization reaction rate has been ignored because it does not directly involve the generation of electrons. In the present study, the influence of non-ionizing reaction rate on the plasma generation mechanism and EM wave attenuation was numerically solved by the plasma flow and multilayer transmission model. According to the simulation results, only the reaction rate of NO rightleftharpoons N + O has a significant effect on the electron number density in all non-ionizing reactions, and the degree of influence is less than the ionization reaction rate. The EM wave attenuation decreases with the decrease of the reaction rate of NO rightleftharpoons N + O. When the reaction rate is reduced by 25 times, the maximum attenuation of electromagnetic wave can be reduced by 12 dB. Finally, a potential scheme by reducing the reaction rate of NO rightleftharpoons N + O was proposed to mitigate the RF blackout problem.

Promoting global stability in data-driven models of quadratic nonlinear dynamics

Modeling realistic fluid and plasma flows is computationally intensive, motivating the use of reduced-order models for a variety of scientific and engineering tasks. However, it is challenging to characterize, much less guarantee, the global stability (i.e., long-time boundedness) of these models. The seminal work of Schlegel and Noack (JFM, 2015) provided a theorem outlining necessary and sufficient conditions to ensure global stability in systems with energy-preserving, quadratic nonlinearities, with the goal of evaluating the stability of projection-based models. In this work, we incorporate this theorem into modern data-driven models obtained via machine learning. First, we propose that this theorem should be a standard diagnostic for the stability of projection-based and data-driven models, examining the conditions under which it holds. Second, we illustrate how to modify the objective function in machine learning algorithms to promote globally stable models, with implications for the modeling of fluid and plasma flows. Specifically, we introduce a modified "trapping SINDy" algorithm based on the sparse identification of nonlinear dynamics (SINDy) method. This method enables the identification of models that, by construction, only produce bounded trajectories. The effectiveness and accuracy of this approach are demonstrated on a broad set of examples of varying model complexity and physical origin, including the vortex shedding in the wake of a circular cylinder.

Magnetosheath plasma flow model around Mercury

Abstract. The magnetosheath is defined as the plasma region between the bow shock, where the super-magnetosonic solar wind plasma is decelerated and heated, and the outer boundary of the intrinsic planetary magnetic field, the so-called magnetopause. Based on the Soucek–Escoubet magnetosheath flow model at the Earth, we present an analytical magnetosheath plasma flow model around Mercury. The model can be used to estimate the plasma flow magnitude and direction at any given point in the magnetosheath exclusively on the basis of the plasma parameters of the upstream solar wind. The model serves as a useful tool to trace the magnetosheath plasma along the streamline both in a forward sense (away from the shock) and a backward sense (toward the shock), offering the opportunity of studying the growth or damping rate of a particular wave mode or evolution of turbulence energy spectra along the streamline in view of upcoming arrival of BepiColombo at Mercury.

CFD-analysis of the interaction of particles with a surface in the conditions of suspension plasma spraying

Gas-thermal coating using suspensions and solutions of precursors allows to obtain promising functional coatings based on oxide ceramics with a controlled microstructure. CFD modeling of air plasma flows generated by the PNK-50 plasmatron in subsonic and supersonic operating modes (diameter of the nozzle 6, 8, 10 mm, gas flow rate of a plasma-forming gas 1 - 7 g / s, flow rate 500 - 2100 m / s). The interaction of single particles of the sprayed material with a size of 0.1 - 5 m with the boundary layer of gas on the surface of the substrate (base) in the process of coating formation was studied, the values ​​of the speed of collision of particles with the base in various spraying modes were obtained. It is shown that the minimum particle size involved in coating formation is 0.5 - 1 m.

Study of RF plasma flow at low pressure: electron temperature influence

A mathematical model of low-pressure RF plasma flow taking into consideration electron temperature influence is presented. Results of calculations of carrier gas velocity, pressure and temperature as well as electron density and electron temperature in plasma flow are showed. Influence of electric field on electron temperature and plasma flow is analyzed.

Investigation of flow regimes in arc plasma–gas interactions using a two-temperature arc in crossflow model

The perpendicular impingement of a gas stream on an electric arc, a configuration known as the arc in crossflow, is of primary relevance in the study of plasma–gas interactions as well as in industrial applications such as circuit breakers and wire-arc spraying. The flow dynamics in the arc in crossflow are the result of coupled fluid-thermal-electromagnetic phenomena accompanied by large property gradients, which can produce significant deviations from Local Thermodynamic Equilibrium (LTE) among electrons and gas species. These characteristics can lead to the establishment of distinct flow regimes depending on the relative values of the controlling parameters of the system, such as inflow velocity, arc current, and inter-electrode spacing. A two-temperature non-LTE model is used to investigate the arc dynamics and the establishment of flow regimes in the arc in crossflow. The plasma flow model is implemented within a nonlinear Variational Multiscale (VMS) numerical discretization approach that is less dissipative and, hence, better suited to capture unstable behavior than traditional VMS methods commonly used in computational fluid dynamics simulations. The Reynolds and the Enthalpy dimensionless numbers, characterizing the relative flow strength and arc strength, respectively, are chosen as the controlling parameters of the system. Simulation results reveal the onset of dynamic behavior and the establishment of steady, periodic, quasi-periodic, and chaotic or potentially turbulent regimes, as identified by distinct spatiotemporal fluctuations. The computational results reveal the role of increasing the relative arc strength on enhancing flow stability by delaying the growth of fluctuating and unstable flow behavior.

Hybrid numerical model of the plasma flow dynamics in open magnetic systems

The report provides a brief overview of the numerical models used to solve plasma physics problems. The necessity of using hybrid models is shown, and a hybrid model that can be used in computer modeling of plasma flows in open magnetic systems is considered in more detail. The features of using hybrid models in two-dimensional cylindrical coordinates are given. To solve the equations of particle motion, the Boris algorithm is considered and its improvement is proposed based on the analytical solution of equations at a time step. We present a number of results of numerical simulation of the interaction of plasma flows obtained on the basis of a hybrid model. The calculations were performed in relation to the conditions of laboratory experiments with laser plasma at the KI-1 facility of the ILF SB RAS and the conditions of the diamagnetic regime at the CAT facility of the INP SB RAS.

Toroidal modeling of thermal particle drift kinetic effects and sub-sonic plasma flow on internal kink mode

The stability of the n=1 (n is the toroidal mode number) internal kink mode in a tokamak plasma is numerically investigated, utilizing the full toroidal, ideal magnetohydrodynamic (MHD) code MARS-F [Y. Q. Liu et al., Phys. Plasmas 7, 3681 (2000)] and the nonperturbative MHD-kinetic hybrid code MARS-K [Y. Liu et al., Phys. Plasmas 15, 112503 (2008)]. This study focuses on two physics effects: the sheared toroidal flow of plasma and the drift kinetic effects from thermal particles (ions and electrons) on the internal kink instability. Within the subsonic flow assumption, the flow and flow shear effects on the internal kink are generally weak, but the kinetic effects can be strong. A significant reduction in the mode growth rate is predicted by the nonperturbative MHD-kinetic hybrid computations, when the precessional drift resonance contributions from both particle species are included and when the mode is not too strongly unstable according to the fluid theory. The stabilization/destabilization of sheared toroidal flow depends on the radial location of the local flow shear. Strong destabilization (stabilization) occurs when a negative (positive) flow shear is located near the q=1 rational surface.

Numerical Modeling of plasma flow in an Electrohydrodynamic thruster with two-cathode electrode arrangement

corona discharge which had been considered undesired before, has become popular for different uses in the past decades; including space thrusters. The basic corona discharge has a simple setup including two electrodes with unequal cross-sections; one of which connected to a high voltage and the other connected to ground or opposite voltage. By changing the number of electrodes, the efficiency of corona discharge can be improved. In this paper, number of electrodes have been changed from 2 to 3 in order to study an electrohydrodynamic thruster. Flow characteristics have been studied by solving the electrostatics and Navier-Stokes equations by finite element method (FEM). The results show that with increasing the number of cathodes the thrust, electric current and thrust efficiency will also increase. In similar condition and geometry, maximum produced velocity resulted by applying any electric potential to anode, increases by about 30% in comparison with one-cathode setup.

Numerical Model of Compression Plasma Flows in Channels under a Longitudinal Magnetic Field

We consider a mathematical model of plasma flows in nozzle channels formed by two coaxial electrodes. The acceleration of plasma in an azimuthal magnetic field is accompanied by its compression and heating in the compression zone at the channel axis past the tip of the shorter central electrode. The mathematical apparatus of the model is based on numerically solving two-dimensional MHD problems using the Zalesak flux-corrected transport (Z-FCT) scheme. In the computations, we study the dependence of the compression phenomenon and its quantitative characteristics on the channel geometry, the problem parameters, and the additional longitudinal magnetic field present in the channel.

13th International Conference on Numerical Modeling of Space Plasma Flows (ASTRONUM-2018)

PREFACEThe Center for Space Plasma and Aeronomic Research (CSPAR) at the University of Alabama in Huntsville (UAH) and Maison de la Simulation, a joint laboratory at the French Alternative Energies and Atomic Energy Commission (CEA), National Center for Scientific Research (CNRS), University of Paris-Sud, and University of Versailles, organized the 13th International Conference on Numerical Modeling of Space Plasma Flows (ASTRONUM-2018) on June 25—29, 2018 in Panama City Beach, Florida, USA.The Program Committee consisted of Tahar Amari (CNRS Ecole Polytechnique, France), Edouard Audit (CEA/CNRS Maison de la Simulation, Gif-sur-Yvette, France, co-chair), Amitava Bhattacharjee (Princeton University, USA), Phillip Colella (Lawrence Berkeley National Laboratory, USA), Anthony Mezzacappa (University of Tennessee, Knoxville, USA), Ewald Müller (Max-Planck-Institute for Astrophysics, Garching, Germany), Nikolai Pogorelov (University of Alabama in Huntsville/CSPAR, USA, chair), Kazunari Shibata (Kyoto University, Japan), James Stone (Princeton University, USA), Jon Linker (Predictive Science, Inc., USA), and Gary P. Zank (University of Alabama in Huntsville, USA).The conference attracted 67 scientists from 14 countries representing different branches of the plasma simulation community. The distinctive feature of this conference is a combination of diverse research topics, all of which are essential for performing high-resolution, continuum mechanics and particle, simulations of physical phenomena in space physics and astrophysics. Among such topics were software packages for modeling and analyzing plasma flows; advanced numerical methods for space and astrophysical flows; large-scale fluid-based, kinetic, and hybrid simulations; turbulence and cosmic ray transport; and magnetohydrodynamics. The applications discussed included cosmology and galaxy formation, supernova explosions, physics of the Sun-heliosphere-magnetosphere environments, theinterstellar medium and star formation, stellar physics, experimental plasma physics, astrophysical accretion, numerical methods for ideal and non-ideal, relativistic and nonrelativistic MHD, etc. The proceedings volume is structured so that it covers all of these topics.

Modeling and simulation of a turbulent‐like thermal plasma jet for nanopowder production

This paper discusses theoretical models and numerical methods to simulate turbulent thermal plasma flow transporting a nanopowder. In addition to a thermal plasma flow model, a sophisticated model is described mathematically for the nanopowder's collective growth by homogeneous nucleation, heterogeneous condensation, and coagulation among nanoparticles, and also transport by convection, diffusion, and thermophoresis, simultaneously. Demonstrative simulations show clearly that a suitable numerical method with high‐order accuracy should be used for long and robust simulation capturing multiscale eddies and steep gradients of temperature, which are the turbulent features of thermal plasma flows with locally variable density, transport properties and Mach numbers. Eddies are first generated at the interfacial region between the plasma jet and ambient nonionized gas by fluid‐dynamic instability. As a result of the eddies' generation–breakup process, the plasma flow entrains the ambient cold gas and deforms its shape traveling downstream. Numerous sub‐nanometer particles are generated by nucleation and condensation in the thin layers near the plasma jet. Those particles diffuse and increase their size, thus decreasing their number by coagulation. Cross‐correlation analysis suggests that the nanopowder distribution distant from a plasma jet can be controlled by controlling the temperature fluctuation at the upstream plasma fringe. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Characterization of the arc in crossflow using a two-temperature nonequilibrium plasma flow model

Diverse industrial applications such as circuit breakers and wire arc spraying involve the interaction between an electric arc and a stream of gas impinging perpendicular to it, a configuration commonly referred to as the arc in crossflow. The arc in crossflow is simulated using a three-dimensional time-dependent two-temperature (heavy-species and electrons) plasma flow model to better capture plasma-gas interactions and deviations from Local Thermodynamic Equilibrium (LTE). The coupled fluid-electromagnetic flow model is solved in a monolithic manner using variational multiscale finite element method. Simulation results are validated with experimental findings and contrasted against results obtained with a LTE model. Results from the two-temperature model corroborate experimental observations while providing quantification of the deviation between heavy-species and electron temperatures. The model is used to characterize the arc in crossflow as a function of the Reynolds and Enthalpy dimensionless numbers, which encapsulate the inter-dependence among the main parameters total current, inflow velocity, and inter-electrode spacing. The characterization revealed the behavior of arc shape, voltage drop, arc power, the degree of nonequilibrium, as well as the characteristic plasma front thickness, with varying controlling parameters.

Non-transferred Arc Torch Simulation by a Non-equilibrium Plasma Laminar-to-Turbulent Flow Model

Non-transferred arc torches are at the core of diverse industrial applications, particularly plasma spray. The flow in these torches transitions from laminar inside the torch to turbulent in the emerging jet. The interaction of the plasma with the processing gas leads to significant deviations from local thermodynamic equilibrium (LTE) far from the arc core. The flow from a non-transferred arc plasma spray torch is simulated using a non-LTE (NLTE) plasma flow model solved by variational multiscale (VMS) and nonlinear VMS (VMSn) methods, which are suitable for unified laminar and turbulent flow simulations. Non-plasma turbulent jet simulations indicate that the VMSn method produces results comparable to those by the dynamic Smagorinsky method, often considered the workhorse for turbulent incompressible flow simulations. VMS and VMSn approaches are applied to the simulation of incompressible, compressible, and NLTE plasma flows in non-transferred arc torch operating at representative conditions found in plasma spray processes. The NLTE plasma flow simulations reproduce the dynamics of the arc inside the torch together with the evolution of turbulence in the produced plasma jet in a cohesive manner. However, the similarity of results by both methods indicates the need for numerical resolution significantly higher than what is commonly afforded in arc torch simulations.

Test cases for grid-based direct kinetic modeling of plasma flows

Grid-based kinetic models are promising in that the numerical noise inherent in particle-based methods is essentially eliminated. Here, we call such grid-based techniques a direct kinetic (DK) model. Velocity distribution functions are directly obtained by solving kinetic equations, such as the Vlasov equation, in discretized phase space, i.e., both physical and velocity space. In solving the kinetic equations that are hyperbolic partial differential equations, we employ a conservative, positivity-preserving numerical scheme, which is necessary for robust calculations of problems particularly including ionization. Test cases described in this paper include plasma sheaths with electron emission and injection and expansion of neutral atom flow in a two-dimensional configuration. A unifying kinetic theory of space charge limited sheaths for both floating and conducting surfaces is presented. The improved theory is verified using the collisionless DK simulation, particularly for small sheath potentials that particle-based kinetic simulations may struggle due to statistical noise. For benchmarking of the grid-based and particle-based kinetic simulations, hybrid simulations of Hall thruster discharge plasma are performed. While numerical diffusion occurs in the phase space in the DK simulation, ionization oscillations are well resolved since ionization events can be taken into account deterministically at every time step.

12th International Conference on Numerical Modeling of Space Plasma Flows: ASTRONUM-2017

PREFACEThe Center for Space Plasma and Aeronomic Research (CSPAR) at the University of Alabama in Huntsville (UAH) and Maison de la Simulation, a joint laboratory at the French Alternative Energies and Atomic Energy Commission (CEA), National Center for Scientific Research (CNRS), University of Paris-Sud, and University of Versailles, organized the 12th International Conference on Numerical Modeling of Space Plasma Flows (ASTRONUM-2017) on June 26—30, 2017 in Saint-Malo, France.The Program Committee consisted of Tahar Amari (CNRS Ecole Polytechnique, France), Edouard Audit (CEA/CNRS Maison de la Simulation, Gif-sur-Yvette, France, co-chair), Amitava Bhattacharjee (Princeton University, USA), Phillip Colella (Lawrence Berkeley National Laboratory, USA), Anthony Mezzacappa (University of Tennessee, Knoxville, USA), Ewald Müller (Max-Planck-Institute for Astrophysics, Garching, Germany), Nikolai Pogorelov (University of Alabama in Huntsville/CSPAR, USA, chair), Kazunari Shibata (Kyoto University, Japan), James Stone (Princeton University, USA), Jon Linker (Predictive Science, Inc., USA), and Gary P. Zank (University of Alabama in Huntsville, USA).