Characteristics of Cold Argon Arc-Jet Plasma Flowing Along Open-Field-Line and the Effects of Collisions on Deceleration

Numerical Study on Acceleration and Deceleration Mechanism of Weakly Ionized Plasma Flowing Supersonically Through Open Field Line

“…It was already shown that the magnetic Reynolds number Re m 0.06 in our experiments [13]. Re m is defined as…”

“…When ions or neutrals come out of the hollow magnet, both of their velocities increase up to about Ma = 2 at z = 0.12 m. After that, they turn into decrease. It is considered that this is due to collisions with residual gas molecules coming from the downstream direction [13]. When we neglect the existence of the residual molecules, this kind of deceleration cannot be reproduced in the present simulation.…”

“…By this apparatus, we found supersonic velocity of ions of helium plasma up to Mach ∼3, and the electric potential drop at the end of the hollow magnets, where the magnetic field became diverging [10]. We also carried out a quasi 1-D numerical simulation based on a fluid dynamic treatment, and found that the ions in the plasma is accelerated both by aerodynamic effect and by electric field induced by the diverging magnetic field [11]- [13].…”

“…We should describe such rarefied systems by the Boltzmann equations, which can be solved statistically by particle-based method, and typically, by the direct simulation Monte Carlo (DSMC) method [14]- [16]. Upon our previous experimental and numerical study [10]- [13], we must carry out numerical simulation of the expanding plasma jet as rarefied gas dynamics based not on fluid approximation but on particle modeling, which is precisely the objective of this paper. As will be shown later, whereas the ions and neutral particles can be treated by particle-based simulation, the electrons cannot be treated by particle model like particle-in-cell (PIC) scheme [17], since required spatial discretization becomes too fine, and the time step also too short.…”

“…We applied rigidsphere model, and therefore, the total cross section was cited from [28], and the probability of charge transfer cross section was set as 1/2 also after Nanbu [28]. Again, for the elastic collision, (12) and (13) are applied, whereas for the charge transfer collision, we set…”