Study on the long-duration shock wave load characteristics of underwater explosion with a tapered long charge initiated at the narrow end

To investigate the spatiotemporal distribution characteristics of underwater explosion shockwave loads from tapered long charges initiated at the narrow end, this paper established a multiphase flow numerical model for underwater explosions based on the Eulerian finite element method, the volume of fluid method, and the programmed burn model. The model's validity was verified experimentally. Numerical simulations revealed directional characteristics of the shockwave: the ignition end exhibited long-pulse width characteristics, while lateral regions formed peak superposition zones. The peak pressure was minimal at 0° but with the longest pulse width, whereas the peak pressure reached its maximum at 100° with the latest arrival time. The explosion process was divided into four stages: top plane ignition, midcourse ignition, pressure unloading, and complete ignition, corresponding to distinct characteristic phases of the long-pulse width shockwave waveform. Adjusting the aspect and radius ratios can modify the waveform of the long-pulse width shockwave but has minimal impact on the shockwave impulse. Increasing the aspect ratio extends both the pulse width and the exponential decay duration of the left peak. The radius ratio primarily affects the slope of the long-pulse width shockwave waveform. Increasing it reduces the left peak value while increasing the right peak value. Finally, the relationship between the long-duration load characteristics of the underwater explosion shock wave of the tapered long charge and the geometric parameters of the explosive was obtained, providing guidance for selecting explosive geometric parameters in underwater explosion experiments with tapered long charges.