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Journal of Fluid Mechanics




Cambridge University Press

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Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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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 Fre a ratio between inertia and gelatine elasticity, resulted in rebound. Higher Fre 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 WeBo phase diagram in water-entry experiments, the elastic Froude number Fre and elastic Grashof number Gre (a ratio between gravity and gelatine elasticity) classify all five different phenomena into distinguishable regimes. We find that Fre 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 Fre values.