Numerical and experimental investigation of the shock and steady state pressures in the bird material during bird strike

The impact of a bird on a structure can, in the first place, be characterized by the pressure exerted on that structure. In bird strike research, the first step towards bird strike modelling is therefore often the investigation of these impact pressures. During impact, two subsequent regimes can be distinguished: a shock and steady state regime. These regimes are characterized by an initially very high shock pressure and a much lower steady state pressure. How relevant the shock regime is during bird strike however can still be questioned. This paper will reveal some key parameters that influence the shock regime, based on the conclusions of several SPH simulations and an experimental test campaign. A zoom on the numerically obtained shock pressure pulse is made, which shows that the impact pressure and duration correspond very well with the theory. Slight tilting of the projectile however can increase the pressure up to 190% of the analytical value. The elastic energy as a measure for the presence of the shock regime is introduced. This shows that the shock regime is relatively negligible for hemispherical ends. The steady state pressures obtained from the simulations are investigated and finally, the analytical values and numerical results are compared to a series of experimental impact pressure measurements with real and (porous) gelatine birds.