Characteristics of multiple cavitations near plate structures in underwater explosions

Abstract

Multiple cavitations generated by near-field underwater explosions can cause significant structural damage, and its generation mechanisms and evolutionary characteristics are still unclear. Therefore, the characteristics of multiple cavitations near plates in underwater explosions are investigated experimentally and numerically. Multiple cavitations near air-backed plates with varying impedances are explored experimentally through a cavitation apparatus, and the effectiveness of Arbitrary Lagrangian–Eulerian method considering multiple cavitations in underwater explosions is validated by the experimental results. Based on the numerical method, the generation processes and evolutionary characteristics of multiple cavitations near air-backed plates at different detonation distances and near water-backed plates with different impedances are analyzed, where the influences of the explosion shock wave and bubble dynamics on evolutionary characteristics of multiple cavitations are commendably elucidated. On the basis of the liquid pressure and structural velocity, the generation mechanisms of multiple cavitations near the structure have also been well revealed. The results indicate that: Ⅰ. The first cavitation is mainly caused by rarefaction wave reflections or transmissions from the structure, which collapses quickly. The second cavitation is driven by negative pressure from liquid stretching due to structural oscillations, which collapses more slowly. Ⅱ. For air-backed plates, decreasing structural impedance increases the first cavitation diameter and delays second cavitation. Smaller detonation distances result in larger diameters and longer durations for cavitations. Ⅲ. For water-backed plates, when impedance is lower than water, cavitation diameters and durations increase as impedance decreases. However, when impedance exceeds water's, cavitation generation becomes difficult. Ⅳ. The third cavitation follows similar generation and evolution patterns as the second. These findings provide theoretical and technical support for revealing the complex mechanical mechanisms in near-field underwater explosions.