Fuel tank wall response to hydraulic ram during the shock phase.

Abstract

THIS Note outlines some preliminary work accomplished in a research program at the Naval Postgraduate School to study the effects of hydraulic ram in fuel tanks upon aircraft survivability and vulnerability. The problem of predicting the interaction of a high speed projectile with a liquid filled tank (hydraulic ram) is a complex but necessary study if kill probabilities are to be predicted for this type of event. Furthermore, to design survivable fuel tanks, it is necessary to understand hydraulic ram in detail. The hydraulic ram phenomenon may be divided into two phases: 1) the shock phase where the projectile exchanges some of its energy with the fluid by the production of a strong, nearly hemispherical shock wave originating from the entry wall, and 2) the cavity phase where further energy is imparted to the fluid by the production and collapse of a vapor filled cavity formed by separation of the fluid from the surface of the projectile as it moves through the tank. This Note considers the shock phase and examines the structural response of the entry wall during this phase.