Asymmetric pulsation characteristics in underwater explosion bubbles from aluminized explosives

The underwater explosion of aluminized explosives presents a prolonged combustion and energy release environment for aluminum powder, which significantly affects the dynamics of bubble expansion and contraction. Conventional bubble prediction models based on the detonation product equations of state (EOS) are therefore inadequate. This study employs Hexanitrohexaazaisowurtzitane (CL-20)-based aluminized explosives to perform underwater explosion experiments in a blast tank while varying aluminum content, particle size, and charge density. The bubble pulsation processes are recorded, revealing asymmetric behavior between expansion and contraction phases. A computational model for underwater explosion bubble loads of aluminized explosives is developed to quantify pulsation asymmetry. This is achieved by formulating the Jones–Wilkins–Lee–AlCombustion (JWL-AlC) EOS, which integrates aluminum combustion processes with the second-order Mach-accurate Lezzi–Prosperetti bubble dynamics equation. The results indicated that, compared to the ideal explosives, the aluminized explosives exhibit substantially shorter bubble expansion times relative to contraction times, demonstrating distinct temporal asymmetry. The proposed model shows strong agreement with experimental observations and effectively calculates the asymmetry characteristics of bubble pulsation. Within the tested ranges, increasing aluminum particle size exerts a negligible effect on bubble expansion and contraction durations. The inclusion of aluminum powder and higher charge density in the aluminized explosives extends both expansion and contraction durations simultaneously, while maintaining their asymmetric behavior.