טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentVeksler Dekel
SubjectStrong Shock Wave Generation Using Underwater Electrical
Wire Explosion
DepartmentDepartment of Physics
Supervisors Professor Yakov Krasik
Professor Emeritus Joshua Felsteiner
Full Thesis textFull thesis text - English Version


Abstract

The purpose of the present research was to investigate an underwater electrical wire explosion (UEWE), namely to determine the efficiency of conversion of the electrical energy deposited into the exploding wire or wire array into the mechanical energy of the generated water flow. The research has been carried out using two different high-current setups, one setup for exploding the wire in microsecond (ms) time scale and the other setup was used for sub-microsecond (sub-ms) UEWE. The ms timescale experiments were carried out using a generator with stored energy of 2.4 kJ, maximum short circuit current of I=74kA and current quarter period of 3.5ms (dI/dt=2.1?1010A/s). The maximal current density (j) that was obtained during ms UEWE is  ~2.2?107A/cm2.

The sub-ms timescale experiments were carried out using a generator with stored energy of 4.3kJ, maximum short circuit current of I = 400 kA and current quarter period of 1ms (dI/dt=4?1011A/s). The maximal current density (j) that was obtained during sub-ms UEWE is ~8?107A/cm2.

Pressure and velocity measurements of the generated SSW were carried out using optical fast streak camera and/or frame photography. Hydrodynamic simulations were extensively used to supplement the experimental data.

Experiments in ms timescale showed the possibility to amplify the shock wave (SW) pressure by almost ~10 times by confining and channeling the SW expansion as well as by the use of zigzag wire configuration.

It was found that the most efficient way to increase the pressure at the front of the SW is by increasing the rate of the energy deposition into a cylindrical exploding wire array. Measurements and simulations carried out in sub-ms timescale of the UEWE showed that one can transfer to the exploded wire up to 85% of the electric energy stored in the capacitors. It was shown that ~15% of the total initially stored energy in capacitors is transferred into mechanical energy of the generated water flow. This 15% of the energy delivered to water flow is distributed between the internal and kinetic energies of the water flow. Namely, 25±5% of the energy delivered to the water flow is the internal energy and the remaining energy is the kinetic energy of the flow. In sub-μs timescale UEWE, we have managed to heat and pressurized the wire up to 3.1eV and 70kBar, respectively. In the case of underwater electrical wire array explosion, the values of velocity and pressure in the water flow at a distance of 100μm from the implosion axis were 3.9 Mach and ~150kBar respectively.