Underwater wire-guided discharges: energy characteristics and pressure impulses

Practical applications of underwater wire-guided spark discharges require detailed knowledge on their characteristics. Although wire-guided spark discharges in water have been studied for several decades, the mechanisms which underpin their development and hydrodynamic parameters still require further investigation. The present paper is focused on the experimental investigation of the pressure impulses generated by underwater discharges initiated with thin copper conductors (50 μm in diameter) and their functional dependency on the parameters of the capacitive pulse driving circuit. Two different lengths of spark initiating wires were used, 2 cm and 3cm. Different combinations of circuit capacitances and charging voltages were used, with the energy available in each discharge being ~16 J in all tests. The functional behavior of the peak magnitude of pressure impulses was obtained for a wide range of capacitance values, from 40 nF to 560 nF with corresponding charging voltages, from 7.6 kV to 28.3 kV. It was shown that the pressure magnitude decreases with an increase in the circuit capacitance (decrease in the charging voltage) with the same energy available per pulse, and this decrease is stronger for the longer length of discharge initiating wires. The results obtained in the present paper will help in further optimization of the wire-guided discharge circuits and topologies for potential practical applications such as rock blasting, recycling and metal forming.