Numerical study on the deformation behaviors of elastic spheres during water entry

Abstract

When elastic spheres enter the water from air, the fluid–structure interaction becomes a complex problem characterized by large deformations. This paper focuses on the deformation behaviors of elastic spheres during water entry. Based on a strong coupling method, a numerical approach to the water entry of elastic spheres is established and validated using the experimental data. In addition to the descriptions of the free surface flows under impacting elastic spheres, the physical mechanism underlying the continuous deformation behaviors of elastic spheres during water entry is also identified. The results show that the magnitude of the prolate deformation is smaller than that of the oblate deformation under the action of hydrodynamic pressure. Additionally, the deformation period of the elastic spheres is related to the material shear modulus, but not to the impact velocity. Previous experimental results describing a linear relationship between the deformation period and the combination parameter for time, D∕(μ0∕ρS)1∕2, are confirmed. The magnitude of sphere deformation is affected by the material shear modulus and impact velocity. The results also show the change characteristics for the kinetic and strain energies of elastic spheres with respect to the water entry time.