  The present paper is dedicated to the development of a numerical model for
the water impact of two-dimensional (2D) and axisymmetric bodies with imposed
motion. The work is a first step towards the implementation of a 2D+t procedure
to be used for the analysis of aircraft ditching. The problem is investigated
under the assumptions of an inviscid and incompressible fluid, which is
modelled by a potential flow model with fully non-linear boundary conditions at
the free-surface. The unsteady boundary value problem with a free-surface is
numerically solved through a boundary element method, coupled to a simplified
finite element method to describe the thinnest part of the jet. The study is
aimed at describing the entry and exit phases. Specific numerical solutions are
developed to tackle the exit phase and to improve the stability of the model.
Results are presented in terms of free-surface shape, pressure distribution and
hydrodynamic load acting on the impacting body. The model is used to study the
water entry and exit of a 2D wedge and an axisymmetric cone, for which
numerical or experimental results are available in the literature. The
numerical investigation shows that the proposed model accurately simulate both
the entry and exit phases. For the exit phase, it is shown that the proposed
model, being fully non-linear, provides a much better prediction of the loads
and the wetted area compared to simplified (analytical) approaches. The effects
of the gravity, usually missing in the approaches available in the literature,
are also investigated, showing they are rather important, especially, in the
exit phase.
