Hydrodynamics of water entry in presence of flow separation from chines

The free surface flow generated during water entry of bodies with hard chines is here investigated in the framework of the potential flow of an incompressible fluid. Attention is mainly devoted to the analysis of the flow generated during the transition from the chine unwetted to the chine-wetted condition, that is when flow separation from the body contour takes place. In order to achieve this goal, the jet developing about the intersection of the free surface with the body contour is carefully described by a simplified hybrid finite element model coupled with the boundary-element approach that is adopted for the solution of the hydrodynamic problem in the whole of the fluid. As soon as the jet tip reaches the separation point, a Kutta condition is applied there, enforcing continuity of the slope of the fluid boundary at that point. Results are presented in terms of free surface shape, pressure distribution and history of the hydrodynamic force throughout the water entry process with particular emphasis on the transition phase.