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Title: Magnetohydrodynamic simulation study of plasma jets and plasma-surface contact in coaxial plasma accelerators

Abstract

Recent experiments by Loebner et al. [IEEE Trans. Plasma Sci. 44, 1534 (2016)] studied the effect of a hypervelocity jet emanating from a coaxial plasma accelerator incident on target surfaces in an effort to mimic the transient loading created during edge localized mode disruption events in fusion plasmas. In this study, we present a magnetohydrodynamic (MHD) numerical model to simulate plasma jet formation and plasma-surface contact in this coaxial plasma accelerator experiment. The MHD system of equations is spatially discretized using a cell-centered finite volume formulation. The temporal discretization is performed using a fully implicit backward Euler scheme and the resultant stiff system of nonlinear equations is solved using the Newton method. The numerical model is employed to obtain some key insights into the physical processes responsible for the generation of extreme stagnation conditions on the target surfaces. Simulations of the plume (without the target plate) are performed to isolate and study phenomena such as the magnetic pinch effect that is responsible for launching pressure pulses into the jet free stream. The simulations also yield insights into the incipient conditions responsible for producing the pinch, such as the formation of conductive channels. The jet-target impact studies indicate the existence ofmore » two distinct stages involved in the plasma-surface interaction. A fast transient stage characterized by a thin normal shock transitions into a pseudo-steady stage that exhibits an extended oblique shock structure. A quadratic scaling of the pinch and stagnation conditions with the total current discharged between the electrodes is in qualitative agreement with the results obtained in the experiments. Finally, this also illustrates the dominant contribution of the magnetic pressure term in determining the magnitude of the quantities of interest.« less

Authors:
 [1];  [1]
  1. Univ. of Texas, Austin, TX (United States). Dept. of Aerospace Engineering and Engineering Mechanics
Publication Date:
Research Org.:
Univ. of Texas, Austin, TX (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1363884
Alternate Identifier(s):
OSTI ID: 1363706
Grant/Contract Number:
NA0002011
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; Journal Issue: 6; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Magnetohydrodynamics; Magnetic fields; Electrodes; Plasma temperature; Plasma jets

Citation Formats

Subramaniam, Vivek, and Raja, Laxminarayan L. Magnetohydrodynamic simulation study of plasma jets and plasma-surface contact in coaxial plasma accelerators. United States: N. p., 2017. Web. doi:10.1063/1.4985320.
Subramaniam, Vivek, & Raja, Laxminarayan L. Magnetohydrodynamic simulation study of plasma jets and plasma-surface contact in coaxial plasma accelerators. United States. doi:10.1063/1.4985320.
Subramaniam, Vivek, and Raja, Laxminarayan L. Tue . "Magnetohydrodynamic simulation study of plasma jets and plasma-surface contact in coaxial plasma accelerators". United States. doi:10.1063/1.4985320.
@article{osti_1363884,
title = {Magnetohydrodynamic simulation study of plasma jets and plasma-surface contact in coaxial plasma accelerators},
author = {Subramaniam, Vivek and Raja, Laxminarayan L.},
abstractNote = {Recent experiments by Loebner et al. [IEEE Trans. Plasma Sci. 44, 1534 (2016)] studied the effect of a hypervelocity jet emanating from a coaxial plasma accelerator incident on target surfaces in an effort to mimic the transient loading created during edge localized mode disruption events in fusion plasmas. In this study, we present a magnetohydrodynamic (MHD) numerical model to simulate plasma jet formation and plasma-surface contact in this coaxial plasma accelerator experiment. The MHD system of equations is spatially discretized using a cell-centered finite volume formulation. The temporal discretization is performed using a fully implicit backward Euler scheme and the resultant stiff system of nonlinear equations is solved using the Newton method. The numerical model is employed to obtain some key insights into the physical processes responsible for the generation of extreme stagnation conditions on the target surfaces. Simulations of the plume (without the target plate) are performed to isolate and study phenomena such as the magnetic pinch effect that is responsible for launching pressure pulses into the jet free stream. The simulations also yield insights into the incipient conditions responsible for producing the pinch, such as the formation of conductive channels. The jet-target impact studies indicate the existence of two distinct stages involved in the plasma-surface interaction. A fast transient stage characterized by a thin normal shock transitions into a pseudo-steady stage that exhibits an extended oblique shock structure. A quadratic scaling of the pinch and stagnation conditions with the total current discharged between the electrodes is in qualitative agreement with the results obtained in the experiments. Finally, this also illustrates the dominant contribution of the magnetic pressure term in determining the magnitude of the quantities of interest.},
doi = {10.1063/1.4985320},
journal = {Physics of Plasmas},
number = 6,
volume = 24,
place = {United States},
year = {Tue Jun 13 00:00:00 EDT 2017},
month = {Tue Jun 13 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
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  • Swirl combustors or burners are found in a wide variety of engineering devices, including furnaces, boilers, and gas turbine engines. Swirl provides an effective means to stabilize the flame, enhance and control the mixing process, increase the combustion efficiency, and eliminate pollutants emission. For achieving design optimization and better performance of the combustors, the properties of swirling turbulent flows should be properly predicted. A numerical simulation of swirling turbulent flows of coaxial jets in a combustor is presented in this paper. The new algebraic Reynolds stress model (ASM) is employed for the closure of the time-averaged governing equations for swirlingmore » turbulent flows. Two cases o the swirling flow, i.e., a coswirl jet flow and a counterswirl jet flow, are simulated. The calculated results of the axial and tangential velocities, static pressure, and turbulent fluctuating velocity are compared with the measured data for both cases. The results illustrate that the predictions by the new ASM are closer to the measurements than those obtained by the {kappa}-{var_epsilon} model.« less
  • Experimental studies by Poehlmann et al. [Phys. Plasmas 17(12), 123508 (2010)] on a coaxial electrode magnetohydrodynamic (MHD) plasma accelerator have revealed two modes of operation. A deflagration or stationary mode is observed for lower power settings, while higher input power leads to a detonation or snowplow mode. A numerical modeling study of a coaxial plasma accelerator using the non-ideal MHD equations is presented. The effect of plasma conductivity on the axial distribution of radial current is studied and found to agree well with experiments. Lower conductivities lead to the formation of a high current density, stationary region close to themore » inlet/breech, which is a characteristic of the deflagration mode, while a propagating current sheet like feature is observed at higher conductivities, similar to the detonation mode. Results confirm that plasma resistivity, which determines magnetic field diffusion effects, is fundamentally responsible for the two modes.« less
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