A Coupling Method for Hydrodynamic Ram Analysis: Experimental and Numerical Investigation

Hydrodynamic pressures generated by a nonexploding projectile penetrating a fuel tank can be very destructive. During the impact, the projectile transfers momentum and kinetic energy to the container through the surrounding fluid. In aerospace industry, hydrodynamic ram effects are identified as an important factor for aircraft vulnerability because fuel tank of the aircraft is the most vulnerable component because the tank represents the largest exposed area to outside projectiles. Understanding the magnitude of the pressure and its distribution inside the tank is critical for designing the structure to survive these incidents. Numerical simulation when validated by tests data is an efficient tool to investigate mechanical phenomena of hydrodynamic ram effects and its damage on the surrounding structure. The main numerical difficulties that can be encountered in this kind of problems and in general penetration problems is the high mesh distortion of the fluid at the fluid-structure interface during projectile penetration. To prevent high mesh distortion of the fluid, a coupling method is used for the fluid as well as a new coupling algorithm is performed at the fluid-structure interface. The coupling method used in the paper has been developed with the collaboration of the first author in the LS-DYNA code and validated for several applications in automotive and aerospace industry for fuel sloshing tank and bird impact problems. In this paper, experimental investigation has been performed and predicted pressure is compared with measured pressure for validation. In addition, modeling parameters such as element size and coupling parameters for the fluid structure coupling are investigated. The purpose of the research is to demonstrate the capability and potential of the fluid structure interaction for simulating this type of problems. Different ways to model reflections of pressure waves off the sidewalls are studied as well. Good correlation is achieved for pressure at specific location inside the water tank.