Application of gurney and flight of fragment calculations for water jet velocities in explosive applications

This study investigates the application of Gurney and flight of fragment equations, typically used to predict metal fragment velocities, in modeling the water jet behavior. Three shotgun cartridge sizes were used as the energy source: 2.59 g, 5.83 g, and 7.13 g. Two configurations were tested: standard (full-barrel water load) and "negative 8" (partial water load). High-speed footage captured water column velocities, and Gurney models, including infinitely tamped and open-faced configurations, combined with the flight of fragment model were used to assess prediction accuracy. Results showed charge strength significantly affects water column velocity, with higher strengths yielding greater stability and velocity retention over distance. The infinitely tamped Gurney model closely predicted experimental velocities, deviating by as little as 1.4% for standard charges and 2.8% for negative 8 charges. Additionally, interesting dynamics such as a 1–2° rise in jet height and the rear overtaking the front was observed. These findings have significant implications for optimizing PAN disruptors and enhancing performance in high-velocity fluid applications and explosive breaching systems.