Slamming dynamics of diving and its implications for diving relates injuries

In nature, many animals dive into water at high speeds; e.g. humans dive from cliffs, gannets plunge, and aquatic animals porpoise and breach. For humans, extreme sports such as cliff diving or high diving provide excitement, but can be close to the limit of bodily injuries. For animals, high dives can provide opportunities to capture prey, escape from predators, or communicate providing a benefit to the diver despite the potential risk of injury. In this study, we demonstrate how similarity in the morphology of diving fronts unifies the slamming force across diving animals. For humans, the evolution of this slamming force depends on the body position at impact, i.e. whether it is a feet-first, head-first or hand-first dive. By measuring a time-averaged impulse on human models, we are able to estimate the unsteady hydrodynamic force that an average human body may experience during the impact phase of a dive, and evaluate whether the force can cause muscle or bone injuries. Thus this study sheds light on a fluid mechanics based protocol for safe high diving and an evolutionary driver for animal morphology.