Two-dimensional water entry and exit of a body whose shape varies in time

The two-dimensional water entry and exit of a body whose shape varies in time in a prescribed way is investigated through analytical and numerical modelling. For this purpose, an analytical model has been developed which extends the modified Logvinovich model of water impact to bodies with time-varying shape. A modified von Karman approach has been developed to describe the exit stage, and a rational derivation of the water exit model which is in use in offshore engineering is presented. CFD simulations are used to assess the accuracy of the analytical model. Several case studies of water entry and exit are presented. The analytical model provides very good force predictions during the entry stage in all cases, but the accuracy of the model in the exit stage depends on the maximum penetration depth. In particular, the appearance of high fluid forces on the body directed downward in both the entry and exit stages is remarkable.