A Numerical-Experimental Comparative Analysis of Water Impact Behaviour of Skin Panels Under Different Impact Conditions

Water impacts of helicopters are likely to have tragic consequences for the passengers of helicopters. Most of the passive safety devices to improve helicopter crashworthiness are designed for ground impact. When impacting a solid or a soft surface, impact loads are rather different and therefore energy absorption devices developed for ground impact are not effective during a water impact. In order to collect reliable data for numerical model validation, water impact drop tests were carried out on a rigid Aluminium alloy thick plate endowed with specifically designed pressure transducers. The tests aimed to measure impact decelerations and pressures considering different impact conditions, i.e. different velocities, impact angles and test article masses. Afterwards, a numerical model of the tests was realized. The fluid region was modelled with Smoothed Particle Hydrodynamics (SPH) method. Applications of SPH method to water impact analysis are not common because of SPH model instability in unbounded regions and difficulties related to finding the correct number of SPH particles. The conditions for SPH model stability were investigated and the accuracy of the overall model was evaluated referring to the data collected in the tests. Eventually, a close experimental-numerical correlation was obtained and guidelines for further investigations were drawn.