  We report on an experimental study of the vertical impact of a concave nosed
axisymmetric body on a free surface. Previous studies have shown that bodies
with a convex nose, like a sphere, produce a well defined splash with a
relatively large cavity behind the model. In contrast, we find that with a
concave nose, there is hardly a splash and the cavity extent is greatly
reduced. This may be explained by the fact that in the concave nosed case, the
initial impact is between a confined air pocket and the free surface unlike in
the convex nosed case. From measurements of the unsteady pressure in the
concave nose portion, we show that in this case, the maximum pressures are
significantly lower than the classically expected "water hammer" pressures and
also lower than those generally measured on other geometries. Thus, the
presence of an air pocket in the case of a concave nosed body adds an
interesting dimension to the classical problem of impact of solid bodies on to
a free surface.
