Liquid spurt caused by hydrodynamic ram

• Fuel tank vulnerability is a major concern of high energy projectile impact.
• The progression of the main spurt of a hydrodynamic ram is described.
• Velocity profiles were determined using Particle Image velocimetry.
• Projectile residual kinetic energy influences the exiting spurts.
• Exit velocity may be dependent on the average velocity difference of the projectile.

The main phase of a spurt produced by a hydrodynamic ram (HRAM) event has been quantified using Particle Image Velocimetry. This highly transient event is induced by the impact and penetration of a high energy projectile into a liquid filled tank, producing an accelerating liquid “spurt” exiting from the projectile entrance hole. This phenomenon is of particular interest to the aircraft survivability community where fuel tank vulnerability and protection is a major concern. The resulting fuel spurt that exits the entrance hole can be highly atomized and flammable and therefore, highly conducive to ignition and fire. It was found that projectile residual kinetic energy levels influenced the shape, magnitude of the velocity profile, and spread of the exiting spurts. Of particular interest is the near field velocity profile of the exiting spurt, where a transition in the velocity profile has been observed. The initial radial spreading of the spurt, as it moves downstream, takes on a reduced spread as the residual kinetic energy increases. Furthermore, the main spurt maintains its axial momentum for a much longer axial transition than that for a self-preserving single phase jet.