Numerical investigation of shock wave characteristics at microsecond underwater electrical explosion of Cu wires

Abstract

Strong shock wave (SW) can be generated during underwater electrical wire explosion as the exploding wire rapidly expands and pushes the surrounding water. In this paper, a coupled model that describes the behaviours of the circuit, the exploding wire, and the evolution of SW was established. Wide range equation of state data and conductivity data were used, making the calculation from solid state possible. The calculated discharge current, voltage, and trajectories of the wire radius and SW front were generally in good agreement with the experimental results, manifesting the validity of the model. Evolution of SW peak pressure, the process of energy conversion, and the effect of the discharge period were studied using the model. Simulation results showed that the radial attenuation of SW peak pressure is largely dependent on wire diameter and energy deposition process, while the efficiency of converting the deposited electrical energy to the mechanical energy of SW is not as sensitive, varying from 40% to 50% tens of microsecond after the current starts. Fast discharge tends to generate SW with higher initial SW peak pressure, while slow discharge enables higher initial energy storage within the limit of insulation and generates SW with slower radial attenuation. The presented model and numerical results could serve as a reference for parameter selection in related applications.

Metal vapor content of an electric arc initiated by exploding wire in a model N2 circuit breaker: simulation and experiment

“…Thus, the maximum velocity for a 40 µm thick copper wire (see figure 10(a)) is 7500 m s −1 , while it is only 650 m s −1 for a 100 µm wire (see figure 11 High-pressure generation further than a few centimeters from the wire requires decreasing the peak pressure attenuation rate by choosing the optimal discharge related to the wire size (0.1 GPa in 4.3 mm from wire at 450 ns in figure 10(c)) or increasing the initial stored energy, otherwise low pressure like what happened in 100 µm EEW will occur. Furthermore, it confirms other research [10].…”

“…A general method for investigating the metal vapor content in an electrically initiated plasma was presented and verified by experiments. Other numerical simulations of the initial plasma formation (PF) in vacuum [9] or underwater [10] are also available. Still, to the authors' knowledge, the method for the calculation of the mixture ratio in high-pressure gases and supercritical fluids (SCFs) presented in this paper has not been published by other researchers so far.…”

“…Heat conduction can also be expressed directly as an energy (loss) source term. So, the equivalent heat conductivity (thc tot ) due to radiation is calculated and is merged in the net emission coefficient (NEC) radiation shown as radii in (8), which is the NEC eestimation of the radiative cooling in W, through PLASIMO ® code [15], which provides a better estimation than others [10]. Q rad (T) is in W. Heat capacity at constant volume, mass density and electrical conductivity of wire in different physical states are defined through ( 9)- (15):…”

Two-dimensional simulation of microsecond-timescale underwater electrical explosion of a copper wire

“…where j(z, r) is current density, σ(z, r) is the electrical conductivity, Q R represents the average radiation loss per unit volume (W m −3 ) which is adopted from [24] as a simplification to avoid detailed radiation transport within the exploding wire.…”

“…More accurate description of UEWE process can be realized by magnetohydrodynamic (MHD) models. Many research institutions including Israel Institute of Technology [18], Imperial College London [19], Institute of High Current Electronics [20], Seoul National University [21], Tsinghua University [22] and Xi'an Jiaotong University [23,24] have developed their own MHD codes; general-purpose MHD codes such as JULIA [25] and ALEGRA [26] were also used to study the UEWE process. Generally speaking, previous studies were usually focused on the exploding wire, for example, to test the accuracy of metal equation of states (EOSs) and conductivity data, to clarify the evolution of the wire state and instabilities, etc, and few on SW characteristics.…”