On the oblique water-entry problem of a rigid sphere

The case of oblique water-entry of a rigid sphere into an ideal incompressible fluid is studied analytically in order to determine the hydrodynamical loads acting on the body. We consider the motion imparted to the fluid by an impulsively-started partially-submerged sphere under the large-impact approximation, in which the free surface is assumed flat and equipotential. Asymptotic small-time expressions are derived for both the vertical and horizontal time-dependent added masses and analytical expressions for the hydrodynamic forces are obtained by differentiating these added masses with respect to the instantaneous submergence depth. The resulting expressions are also compared with corresponding numerical solutions and with a known solution for a two-dimensional profile.