Modeling the Free Surface Penetration of Cylinders and Spheres

Free surface penetration is a multiphase flow problem whereby a solid body is translated through a gas penetrating a liquid. The nature of the ensuing fluid dynamics poses a highly complex analytical modeling effort. It is known that for a given surface roughness, body geometry, and velocity, a cavity can be formed aft of the body and maintained for a given distance with traveling from air into water. An analytical model [Dynamics of Transient Cavities, V. Duclaux et al.] of the classical free surface penetration of spheres and cylinders and computational simulations using ANSYS CFX version 12 are preformed and presented. Comparisons of the pinching (closure) and cavity radius as a function of time are considered and the effect of surface roughness is explored.