The shock wave and bubble evolution characteristics of a charge enveloped by a spherical air layer

High-speed vehicles traveling in water will be enveloped by supercavitation, which will have a significant effect on the explosion loads produced by the charge. Therefore, the characteristics of shock wave load, bubble evolution, and bubble loads in underwater explosion when the charge is enveloped by a spherical air layer are investigated using the multi-material Euler method. The effectiveness of the numerical method in simulating shock waves and bubble dynamics is validated by conducting an underwater explosion experiment. The influence of the enveloping air layer and its thickness on the characteristics of underwater explosion loads is analyzed. Besides, a theoretical formula is developed to calculate the transmitted and reflected pressure on the air–water interface, and a predictive formula for the transmitted shock wave peak pressure in water is derived, which are in good agreement with numerical results. These findings demonstrate that multiple pressure waves will be generated when the charge is enveloped by a spherical air layer, and the irregular bubble surface will be formed after the fusion of detonation products and enveloping air. The spherical air layer will diminish the shock wave load and bubble pulsation pressure, and increase the bubble radius and pulsation cycle.