In order to model this event, a fully coupled fluid-structure interaction analysis is required. A building block approach was used where increasing complexity of the event was captured in the models. Specifically, the results are in the form of pressure iso-surfaces within the fluid and deformations, and failures in the structure. Although the analysis was performed on a small structural article, the insights and lessons learned will be invaluable to future work planned in modeling a full-scale wing. Statistics show that HRAM is the most deadly of these three mechanisms.
Hydrodynamic ram is the phenomenon that occurs when a fuel tank is ballistically impacted.
Since the fuel is nearly incompressible, the energy imparted to it is applied to the aircraft structure as pressure. This situation is significantly worsened if the impactor carries an explosive charge that detonates within the fuel. In addition to the high initial pressures resulting from hydrodynamic ram, the complex fluid-structure interaction that occurs often serves to redirect internal pressure waves and can significantly change the damage experienced by the aircraft wing. This results in a highly complex phenomenon that is unique for each particular structural arrangement and impact location. Because the HRAM problem is multi-disciplinary in nature, the authors concerned themselves with issues relating not only to fluid and structural modeling, but to the interface as well.