Simulation on Electrostrictive-force induced Cavitation Formation Process in Cyclohexane

Abstract

Streamer, known as the pre-breakdown process, has been widely studied in insulating liquids such as mineral oil. Due to the complexity of the composition of mineral oil, cyclohexane, a simple hydrocarbon-based liquid is often used in some fundamental studies. The mechanism during streamer initiation stage may differ under different voltage rising rates. Cavitation is likely to form under fast-rising voltage, which helps to trigger streamer initiation due to the acceleration of electrons inside the cavities. This paper simulates the electrostrictive force induced cavitation formation process in cyclohexane and its influencing factors. Cyclohexane is considered as compressible liquid. The threshold of cavitation formation in cyclohexane is estimated to be −6 MPa. Coupled Poisson equation and Navier-stoke equations are solved by finite element method in COMSOL Multiphysics for cavitation formation simulation. A needle-plane geometry is used and different voltage rising rates are modelled. Simulation results show that it is possible for electrostrictive force to lead to cavitation formation in the vicinity of needle tip in cyclohexane under fast rising voltage. The liquid is pushed towards the needle tip due to the electrostrictive force. Voltage application with slower rising rate leads to more liquids to move but requires higher voltage magnitude to form cavitation. The absolute value of the minimum magnitude of negative pressure in cyclohexane increases with the increase of voltage rising rate.