Motion response induced by air cushioning effect during the water impact of a plate at small deadrise angles

When a flat plate impacts water at small deadrise angles, its rotational motion is dominated by the asymmetrical air cushioning effect underneath the plate. In the regime of impact velocity and deadrise angle, four typical motion patterns are found: pitching-down, fluctuating-pitching-down, pitching-up-down, and pitching-up. These motions are mainly dictated by two physical processes of asymmetrical air cushioning effect: keel compression and edge compression. In keel compression, the air underneath the keel is compressed and produces a pitching down moment; in the following edge compression stage, the air underneath the edge is heavily compressed and produces a strong pitching up moment.