Investigation on anode plume in high-current vacuum arc by experiments and simulations
PHYSICS OF PLASMAS
Authors: Wang, Lijun; Yan, Chao; Yang, Ze; Zhang, Tuo; Wang, Kai; Jia, Shenli
Abstract
The objective of this paper is to investigate anode plume in high-current vacuum arc through experiments and simulations. A series of experiments are carried out in a demountable vacuum chamber at different current levels with the CuCr40 contact. Combined with arc voltage and arc image, the formation and evolution of typical anode modes, especially anode plume, are analyzed. The contact erosion and scanning electron microscopy (SEM) results are also discussed after experiments. Based on the experimental results, a two-dimensional (2D) magneto-hydro-dynamic (MHD) model is adopted to study the physical characteristics of anode plume. The experimental results show that a larger current leads to a more intense anode mode forming at smaller gap distance with a bigger and brighter arc column. Anode plume is generated between anode spot type 2 and current zero due to the obvious pressure difference between anode vapor and cathode plasma, which is confirmed by the simulation results of different anode temperatures. The contact erosion is more severe in the area where anode plumes frequently appear. The spatial distribution of number density, temperature, pressure, and electrical conductivity of anode plume are analyzed by simulations, and therefore the related experimental phenomena are explained. Published under license by AIP Publishing.
On the problem of steady bifurcation of a falling sphere in a Navier-Stokes liquid
JOURNAL OF MATHEMATICAL PHYSICS
Authors: Galdi, Giovanni P.
Abstract
We study steady bifurcation for the coupled system body-liquid consisting of a sphere freely falling in a Navier-Stokes liquid under the action of gravity. In particular, we show that, under the assumption that for the bifurcating solution, the translational velocity of the sphere is parallel to the gravity, bifurcation takes place, provided that 1 is a simple eigenvalue of a suitable linear operator and the transversality property holds. Moreover, we also give sufficient conditions for symmetry breaking. Published under license by AIP Publishing.