Measuring Underwater Blast Waves from Copper Wire Explosions with High-Resolution Pressure Data

What is it about?

Blast waves resulting from underwater electrical wire explosions (UEWEs) are characterized using a high-speed camera and a hydrophone. The UEWEs are created by discharging a 10 μF pulsed power generator that delivers currents up to 170 kA to copper wires on a microsecond timescale, thereby driving their rapid phase transitions from solid to plasma. The trajectory of the resulting cylindrical blast waves is captured by a 5-Mfps high-speed camera, which forms part of a z-type shadowgraphy system. Pressure profiles of the blast waves are measured with a fiber optic hydrophone at 6, 8, and 10 mm away from the exploding copper wires of 150, 400, and 500 μm in thickness. Good agreement is found between these experimental results and simulations, which couple a zero-dimensional (0D) magnetohydrodynamic model for the wire expansion and a one-dimensional (1D) Euler model for the blast wave propagation. The simulations provide experimentally inaccessible insight into the first microseconds of the explosion, including the wire's thermodynamic and electrical properties, and the energy transfer dynamics between the wire and water. This reveals how wire diameter affects the transfer of electrical energy to the blast wave with 150 μm wires leading to underdamped electrical dynamics that generate slower blast waves and lower pressures than 400 and 500 μm wires. Overall, the experiments demonstrate blast pressures up to 500 MPa measured at 6 mm from the 500 μm wire and Mach numbers reaching 1.92 at 3 mm from the explosion center.

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Photo by Marko Sellenriek on Unsplash

Photo by Marko Sellenriek on Unsplash

Why is it important?

This study characterizes underwater electrical wire explosions (UEWEs) as a safe, controllable source of intense blast waves. Using 5 Mfps shadowgraphy and fiber-optic hydrophones, it measures blast trajectories and pressures from copper wires of varying diameters. Coupled simulations, combining magnetohydrodynamic wire expansion with fluid dynamic shock modeling, reveal early-stage energy transfer mechanisms. The work validates predictive models and provides a repeatable platform for high-pressure hydrodynamics research, with implications for underwater engineering, defense applications, and energy system design.