Modelling of metallic jet production using pulsed underwater discharges

We have used pulsed electrical discharges in water to accelerate thin conical metallic foils to velocities of 1.4-1.5 km/sec. The foils turn into high-velocity jets, which can perforate metal sheets. Experimental results are reported in a companion paper in this conference. In this paper, we report on computer simulations for such systems. The simulations have been done using a two-dimensional, time-dependent, finite-difference, lagrangian hydrodynamic code, which includes strength-of-material effects. The simulations yield the temporal evolution of the projectile shape and the velocity distribution along its length. They also yield the spatio-temporal profiles of density, temperature and velocity of the working fluid (water) and the casing. A preliminary parametric study has been performed for this system, studying the effect of cone indentation and liner thickness on projectile behaviour. The simulations show the formation of projectiles with large velocity gradients along their length. Jet velocities predicted by simulations are generally lower than those observed in experiments. However, after allowance is made for differences in cone angles and liner thickness, the predictions appear to be consistent with experiment.