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.

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Circuit inductance is an important parameter at underwater electrical wire explosion (UEWE) experiments as it closely relates to the energy deposition rate to the load wire. In this study, the circuit inductance was varied within a wide range from 1.55 μH to 93.2 μH by inserting inductive coils to study its effects on electrical and shock wave (SW) characteristics at UEWE. Experimental results showed that UEWEs using thinner wires were less affected by the increase of circuit inductance and the SW peak pressure several-cm away from the wire is not sensitive to the increase of circuit inductance if properly choosing the diameter of load wire: the maximum SW peak pressure obtained with varied diameter (constant energy storage and wire length) only saw a decrease of 30% as the circuit inductance increased by 60 times from 1.55 μH (0.3 mm diameter, 19 MPa) to 93.2 μH (0.2 mm diameter, 13 MPa). Hydrodynamic calculations were used to explain the experimental results. These results indicated that for a practical UEWE system, the energy storage can be far away from the load while keeping an acceptable loss of the capability of generating strong SWs, which greatly improves the flexibility of system designing for example by enabling much larger energy storage for certain harsh working environments.

The underwater electrical wire explosion (UEWE) is an appealing source of underwater shock waves (SWs) with a high conversion efficiency from electrical energy to mechanical energy, good repeatability and controllability. Industrial applications are already seen in oil-well unblocking and stratum stimulation, and research is currently underway to apply UEWEs in electro-hydraulic forming, exploitation of unconventional gas and oil resources, etc. The emerging new applications call for a review on UEWE research from the perspective of an efficient SW source. This review paper considers the physical processes and numerical simulation methods, electrical and SW characteristics, and current and potential applications, and provides suggestions for future research directions. The code (XJ_UEWE01) developed by the authors to solve a coupling model of UEWE is included. The paper will provide students and researchers new to this field with an explanation of basic concepts of UEWE and a detailed overview of previous studies, and will aid research on UEWE applications, especially device development and parameter optimization.

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