Viscoelasticity dependence on hydrodynamic responses during water entry

With the diversification of materials required in the aerospace field, the water entry problem with moving bodies is no longer limited to traditional rigid materials. The viscoelasticity dependence on hydrodynamic responses during the vertical water entry of three-dimensional spheres is computationally and experimentally investigated at low Froude numbers. Upon free surface impact, the dynamic stress of spheres and free surface pressure are dependent on the structural viscoelasticity, and the physical mechanisms are elucidated from the elastic wave propagation and impact energy absorption in the sphere. Additionally, the dynamic stress during water impacts can be predicted from the material properties of impacting spheres. During the water movement, cavity formations at low impact velocity are hardly dependent on the viscosity, but the sphere viscosity at high impact velocity can promote chaos on the cavity walls. The results also show that the viscosity of spheres can affect the deformation behaviours and wetted areas of spheres during water entry. Under a given variation in the material shear modulus, the effect of the sphere viscosity on cavity formations and sphere deformations during water entry can be qualitatively predicted.