Theoretical and experimental study of bubble dynamics in underwater explosions

The development of analytical theory and experimental methods for understanding the correlation between the explosive properties and bubble dynamic characteristics in underwater explosions has important engineering application value for underwater weapons and ships. Based on the assumption of an instantaneous explosive detonation, we introduced the Jones-Wilkins-Lee equation of state to describe the high-pressure state in an explosion bubble and established the initial conditions for the bubble dynamics calculations. Considering the high-Mach-number flow and high pressure at the initial boundary of the explosion bubble, the Lezzi-Prosperetti equation with second-order Mach accuracy was used. Thus, an analytical model and a calculation method of the explosion bubble dynamics for an explosive detonation were established. This direct link between the detonation parameters and the bubble features is significant for the subtle design, selection, and optimization of explosives' properties. A micro-equivalent explosive bubble pulsation experiment was carried out in a water tank using a customized experimental system, which can offer nearly boundary-free condition to mitigate the reflective wave effects on bubbles. Three types of explosives were used in the experiment: the Research Department explosive (RDX), the Pentaerythritol tetranitrate (PETN), and the Hexanitrohexaazaisowurtzitane (CL20). Finally, the experimental results and the practicability of the experimental system were analyzed. The influence of the explosive type on the dynamic characteristics of the explosion bubbles and the differences between the theoretical and experimental results were compared. The results showed that the proposed explosion bubble dynamics model and calculation method have high accuracy and practicability. The proposed model can be used for explosives with known detonation parameters and equation of state parameters. The detonation parameters, velocity, and pressure are linked to the bubble features pulsation period and the maximum radius directly. The designed experimental system, which is capable of simulating an infinite water for the explosion of micro-equivalent explosives, was stable and easy to use. The work is significant for the subtle design, selection, and optimization of explosives' properties.