A refined numerical investigation of a large equivalent shallow-depth underwater explosion

TL;DR

This paper presents a detailed numerical analysis of shallow-depth underwater explosions, validating the model against theoretical and experimental data, and exploring cavitation effects, bubble dynamics, and the influence of gravity.

Contribution

It introduces a refined numerical model incorporating cavitation and free surface effects, providing new insights into shallow-depth underwater explosion dynamics.

Findings

Numerical results agree well with theoretical and experimental data.

Cavitation effects significantly influence flow-field pressure.

Gravity's impact on bubble dynamics varies with initial conditions.

Abstract

The large equivalent shallow-depth explosion problem is very significant in the field of naval architecture and ocean engineering, as such explosions can be used to attack and demolish ships and anti-ship missiles. In the current work, a refined numerical study of the flow-field characteristics of a large equivalent shallow-depth explosion is carried out using a self-developed Eulerian finite element solver. Firstly, the numerical model is validated against theoretical results and a small equivalent explosion test in a tank. The numerical results are found to agree well with the theoretical and experimental results. In the next step, the cavitation cut-off effect is added to the underwater explosion model, and the cavitation phenomenon is quantitatively analyzed through the flow-field pressure. In addition, the dynamic characteristics of the bubble and water hump under various initial conditions for different stand-off parameters are analyzed. The effect of gravity on these physical processes is also discussed. The bubble pulsation period, taking into account the free surface effect, is then quantitatively studied and compared with Cole's experimental formula for an underwater explosion. Overall, when the stand-off parameter > 2, the influence of the free surface on the empirical period of the bubble is not significant. Our investigation provides broad insights into shallow-depth underwater explosions from theoretical, experimental, and numerical perspectives.