Slamming dynamics of diving and its implications for diving-related injuries

Abstract

In nature, many animals dive into water at high speeds, e.g., humans dive from cliffs, birds plunge, and aquatic animals porpoise and breach. Diving provides opportunities for animals to find prey and escape from predators and is a source of great excitement for humans. However, diving from high platforms can cause severe injuries to a diver. In this study, we demonstrate how similarity in the morphology of diving fronts unifies the slamming force across diving animals and humans. By measuring a time-averaged impulse that increases linearly with the impact height, we are able to estimate the unsteady hydrodynamic forces that an average human body experiences during the slamming phase of a feet-first, hand-first, or head-first dive. We evaluate whether the unsteady forces put the diver at risk of muscle or bone injuries for a particular diving height. Therefore, this study sheds light on a hydrodynamics-based protocol for safe high diving and an evolutionary driver for animal morphology.

Slamming forces during water entry of a simple harmonic oscillator

“…Beyond informing engineering applications, such forces can prove fatal for human divers if the hydrodynamics are not respected (Pandey et al. 2022).…”

“…Other impactors such as aerospace structures (Seddon & Moatamedi 2006) or amphibious autonomous vehicles (Siddall & Kovač 2014;Shi et al 2019b) have benefited from advancements in the area. Beyond informing engineering applications, such forces can prove fatal for human divers if the hydrodynamics are not respected (Pandey et al 2022).…”

Air cavity deformation by single jointed diver model entry bodies

“…Competitive divers perform hands first entries such as the rip entry maneuver from heights below 15 m to prevent injury [22]. Consider an Olympic diver performing a dive from the 10 m platform with an impact speed of approximately 16 m/s.…”

“…It can be especially helpful to understand what impact forces organisms can withstand and what drop height would cause injury. The impulse force generated at impact for a variety of animals can be predicted by corresponding simplified geometries [22]. Experiments found that birds choose to plunge dive at speeds that keep them within a safe regime [23].…”

Effect of feathers on drag in plunge‐diving birds

“…In nature, some animals exhibit diving behaviors with diverse body shapes and surface coverings that have evolved to optimize their interaction with water. 1,2 When an animal dives the shape of the diving front significantly influences the forces encountered; a blunt front tends to increase drag and impact force, whereas a sharp, narrow front can reduce these forces. 3,4 Over evolutionary timescales, these pressures have the potential to alter animal morphology, driving adaptations that minimize resistance and impact during diving.…”