Water entry of flexible impactors*

The problem of high-speed water entry is fundamental to a number of engineering and naval applications and has been the subject of extensive study over the past century. Despite such advances, the role of impactor compliance has received very little attention, and may play a role in biological divers such as sea birds. We present experiments on the normal impact of a two degree-of-freedom flexible body onto a pool of water. An axisymmetric nose is connected to the impactor body via a linear spring and damper. We report direct impact force measurements over a range of spring stiffnesses, damping coefficients, and impact velocities. Notably, we observe a reduction in peak impact force for the flexible system as compared to an equivalent rigid impactor. Other qualitative observations and preliminary modeling results will be discussed.