Investigation on bubble load characteristics of near-field underwater explosion

Abstract

The wall pressure generated by near-field underwater explosion bubble involves significant nonlinear problems. This has been the focus and difficulty of the research on the anti-explosion design of battleships. To quantify the load characteristics of bubble pulsation and water jet pressure, underwater explosion tests were conducted beneath a clamped square plate subjected to 2.5g TNT at different distances (R = 10, 15, 20, 22.5, and 25 cm). Results showed that as the stand-off distance increased to the maximum radius of the bubble, there was a peak value of the impulse for bubble pulsation and water jet. A finite element model was then established and benchmarked. The benchmarked model was used to further explore the load characteristics of the bubble pulsation and water jet, considering the effect of the stand-off distance, plate dimension, horizontal distribution, and explosive equivalent. It was found that: a) as the plate dimension increased, the pressure of the shock wave to the plate was basically unchanged, while the period and impulse of the bubble pulsation and water jet decreased; b) the impact of the water jet pressure was concentrated within 6.72 times the radius of the explosive. Finally, an empirical formula was proposed to predict the impulse of the bubble pulsation and water jet. This research is able to provide guidance to investigate the blast resistance of ships.