Numerical Simulation of Cathode Microcrater Formation on Electrode Surface Based on Smoothed Particle Hydrodynamics

Vacuum arc is a typical discharge phenomenon that always occurs in high-voltage vacuum gaps of vacuum system. The vacuum arc could cause local erosion of material on the electrode surface, which would reduce the dielectric strength of the vacuum gap and affect the stability and security of the high-voltage vacuum system. Cathode microcraters with diameters of several microns would form during the burning process of vacuum arc, and this hydrodynamics processes also play a key role in the development of arc discharges. However, previous simulations of the dynamic processes of cathode microcrater formation still have shortcomings in computational efficiency and numerical accuracy. In this paper, an improved smoothed particle hydrodynamics (SPH) method is proposed to study the formation mechanism of cathode microcrater on electrode surface under vacuum arc. First, the improved SPH method is proposed by introducing the free-surface detection algorithm, the surface tension model and the current continuity equation into the basic SPH method. Then, the dynamic processes of the cathode microcrater formation are simulated based on the improved SPH method. Furthermore, the mechanism and characteristics of the microcraters are analyzed. In addition, the effects of the external parameters such as plasma pressure and energy flux density on the microcraters are quantitatively studied and discussed. The simulation results show that the local cathode material would be melt under the effect of plasma pressure and energy flux density of vacuum arc and hence forming a liquid metal pool on the cathode surface. The molten metal would sputter under the action of high pressure and thus form a microcrater on the cathode surface. Besides, the liquid metal jet could break and form droplets under some circumstances. The results of this paper may provide a new approach for further studying the formation mechanism of cathode microcrater and the electrode surface erosion.