Experimental study on splash behaviors and cavity shape of elastic spheres during water entry

At present, there are sufficient studies on the splash formations and cavity dynamics during the water entry of rigid bodies, but few related researches on elastic spheres. In this paper, the water entry behaviors of elastic spheres with different impact velocities and shear moduli are experimentally investigated. In splashing experiments, we observe that the elasticity of sphere can affect the splash formation. Before the formation of the curtain dome-over, the wider and higher splash curtain is formed by the elastic sphere with lower shear modulus. With the increase of the shear modulus, the curtain dome-over occurs later. In addition, we have shown the change characteristics for the sealing time of splash with the dimensionless ratio of material shear modulus to impact hydrodynamic pressure. In cavity dynamics experiments, the shapes of cavities formed by elastic spheres are classified. By accounting for the radial motion of the cavity wall, the basic physics of the three typical cavities are elucidated. Our results also show that the dimensions of the cavity closure scale with the Froude numbers. Based on the morphological classification of cavity, the shape of cavity can be predicted from the material properties and impact conditions.