Analysis of Bubble Dynamics Created by Ballistic Impacts in Liquid-Filled Tanks

Abstract

In the event of impacts of high speed/high energy projectiles in liquid-filled tanks, the container may suffer large hydrodynamic loads that could possibly rupture the entire structure. This impact scenario is referred as hydrodynamic ram (HRAM) in the literature. To design an aircraft fuel tank that resists such HRAM events is a particularly difficult task due to structural optimization constraints that already exist in aeronautics (weight, range, etc). HRAM events are generally characterized by four stages: the shock stage (Fig. 1, t = 0 ms), the drag stage (Fig. 1, t = 0.2 ms), the cavity growth stage, and the collapse stage (Fig. 1, t = 2.5–4.5 ms). The ballistic projectile first penetrates the container and creates a shock wave that propagates in the liquid. Then a cavity bubble is created in the wake of the projectile. The growth and collapse of this bubble induce large hydrodynamic loads on the container structure that are hardly measurable during complex and expensive experiments.