Multiple Birdstrike Analysis : a Survey of Feasible Techniques

Statistics show that, despite the efforts provided to avoid collisions between aircraft and birds, birdstrike still represents a threat for flight safety. Therefore, aircraft components, before being allowed into operational use, have to be certificated for a proven level of bird impact resistance. Characteristic features of the birdstrike such as the coupling between impact loads and structure response gave a significant impulse to the development of numerical techniques that could replace the costly experimental tests. In particular, the explicit codes based on the Finite Element Method have shown to be a valid tool to develop high efficiency bird-proof structures. Nevertheless, when simulating such an event, these codes suffer the huge distortions of the mesh and, therefore, events such as a multiple bird impact are still out of the reach of these codes. In the years, alternative approaches to the problem have been proposed. In particular, different models of the bird such as those related with the Eulerian/Arbitrary Lagrangian Eulerian approach or with the Smoothed Hydrodynamic Method have been proposed. In this work, the impact of two birds against the inlet of a modern large-size aircraft has been considered. Using LSTC LS-Dyna, four different bird models have been investigated: Lagrangian Finite Element, Arbitrary Lagrangian Eulerian, Smoothed Particle Hydrodynamic, and nodal masses model. The obtained results were compared one with the others and eventually advantages and disadvantages of the different models have been highlighted and discussed.