Gelatine cavity dynamics of high-speed sphere impact

We investigate the impact and penetration of a solid sphere passing through gelatine at various impact speeds up to. Tests were performed with several concentrations of gelatine. Impacts for low elastic Froude number, a ratio between inertia and gelatine elasticity, resulted in rebound. Higher 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 - phase diagram in water-entry experiments, the elastic Froude number and elastic Grashof number (a ratio between gravity and gelatine elasticity) classify all five different phenomena into distinguishable regimes. We find that can be a good indicator to describe the cavity length, particularly in the shallow-seal regime. Finally, the evolution of cavity shape, pinch-off depth, and lower cavity radius are investigated for different values.