Abstract
We investigate the impact and penetration of a solid sphere passing through gelatine at various impact speeds up to 143.2 m s(-1). Tests were performed with several concentrations of gelatine. Impacts for low elastic Froude number Fr-e, a ratio between inertia and gelatine elasticity, resulted in rebound. Higher Fr-e values resulted in penetration, forming cavities with prominent surface textures. The overall shape of the cavities resembles those observed in water-entry experiments, yet they appear in a different order with respect to increasing inertia: rebound, quasi-seal, deep-seal, shallow-seal and surface-seal. Remarkably, similar to the We-Bo phase diagram in water-entry experiments, the elastic Froude number Fr-e and elastic Grashof number Gr(e) (a ratio between gravity and gelatine elasticity) classify all five different phenomena into distinguishable regimes. We find that Fr-e can be a good indicator to describe the cavity length H, particularly in the shallow-seal regime. Finally, the evolution of cavity shape, pinch-off depth, and lower cavity radius are investigated for different Fr-e values.