Formation of self-organized anode patterns in arc discharge simulations

Abstract

Pattern formation and self-organization are phenomena commonly observed experimentally in diverse types of plasma systems, including atmospheric-pressure electric arc discharges.However, numerical simulations reproducing anode pattern formation in arc discharges have proven exceedingly elusive. Time-dependent three-dimensional thermodynamic nonequilibrium simulations reveal the spontaneous formation of self-organized patterns of anode attachment spots in the free-burning arc, a canonical thermal plasma flow established by a constant DC current between an axi-symmetric electrodes configuration in the absence of external forcing. The number of spots, their size, and distribution within the pattern depend on the applied total current and on the resolution of the spatial discretization, whereas the main properties of the plasma flow, such as maximum temperatures, velocity, and voltage drop, depend only on the former. The sensibility of the solution to the spatial discretization stresses the computational requirements for comprehensive arc discharge simulations. The obtained anode patterns qualitatively agree with experimental observations and confirm that the spots originate at the fringes of the arc -anode attachment. The results imply that heavy-species -electron energy equilibration, in addition to thermal instability, has a dominant role in the formation of anode spots in arc discharges.

Observation of fine-ordered patterns on electrode surfaces subjected to extensive erosion in a spark discharge

“…The formation of patterns on surfaces subjected to electrical discharges has been reported for glow discharges (GD), arc discharges and dielectric barrier discharges (DBD) (Astrov, Ammelt, Teperick, & Purwins, 1996;Gurevich, Zanin, Moskalenko, & Purwins, 2003;Trelles, 2013;Hontañon et al, 2014). A considerable amount of work towards the modeling of pattern formation can also be found in the literature, with regard to both for the generalized process (Cross & Hohenberg, 1993;Turing, 1952) as well as for certain special electrical discharges (Almeida & Benilov, 2013;Müller, 1988;Trelles 2014).…”

“…A considerable amount of work towards the modeling of pattern formation can also be found in the literature, with regard to both for the generalized process (Cross & Hohenberg, 1993;Turing, 1952) as well as for certain special electrical discharges (Almeida & Benilov, 2013;Müller, 1988;Trelles 2014). The patterns described therein are diverse and comprise regular arrangements of dots (Astrov et al, 1996), lines and concentric circles (Gurevich et al, 2003).…”

“…Astrov et al, 1996;Gurevich et al, 2003;Müller, 1998), or (b) first-principle modeling of gas discharges (e.g. Almeida & Benilov, 2013;Trelles, 2013Trelles, , , 2014). Trelles has recently reported about non-LTE simulation results for arc discharges in the pin cathode-plane anode configuration (Trelles, 2014) and found that the anode pattern formation is strongly affected by the current as well as the anode cooling.…”

“…Almeida & Benilov, 2013;Trelles, 2013Trelles, , , 2014). Trelles has recently reported about non-LTE simulation results for arc discharges in the pin cathode-plane anode configuration (Trelles, 2014) and found that the anode pattern formation is strongly affected by the current as well as the anode cooling. The number, size and location of the spots was found to be markedly current-dependent.…”

“…Trelles suggested that the pattern formation is due to an imbalance between the heat lost by the heavy species to the electrode and current transfer by electrons. It was also stated that the presence of competing processes is a common characteristic of self-organization phenomena (Benilov, 2014;Trelles, 2014). Recently a cluster issue of Plasma Source Science and Technology was specifically dedicated to the topic of 'Spots and patterns on electrodes of gas discharges' (Volume 23, Issue 5, October 2014).…”