Deep Dive: An Investigation into How Divers Use Dynamic Shape Change to Reduce Splash
Open AccessDivers at all levels of competition strive to perform the rip entry maneuver to reduce their visible splash and receive higher scores. To perform a rip entry divers roll their body in a somersault after impact — dynamically changing their shape from a slender body to a bluff body. This shape change after impact separates divers from previously studied entry bodies. It is well documented that different characteristics of the impacting body, such as impact velocity, frontal geometry, and underwater trajectory, will produce different shapes and sizes of the splash and air cavity created during the entry event. However, the fluid dynamics mechanism that allows divers to achieve a splash-less entry by performing the rip entry maneuver is, so far, unexplained. In this study, a geometrically simplified diver model is developed to perform a passive roll after entry that mimics the rip entry maneuver. Experiments capture the entry event of this model with a high speed camera. The deformation after impact, estimated size of the air cavity, and splash production are analyzed. Models that deform are found to have an estimated air cavity 42%-154% larger than their fixed counterparts. The deformation of the hinged model is found to change how the trailing air cavity re-attaches to the legs during entry. The velocity of the diver model after impact is found to significantly change the splash, reducing theWorthington jet by up to 60%. By performing the rip entry divers are undergoing dynamic shape change and rapidly decelerating. Two computational cases are investigated to identify how deceleration afterimpact changes the splash. A 48% decrease in splash height is reported for the fixed model that decelerates after impact. Our results demonstrate that the rip entry reduces visible splash for divers due to the deceleration and dynamic deformation after impact. These results can be used to help divers more consistently achieve splash-less entries and be applied to the design of mechanical systems that enter the water without creating a visible splash.
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Gregorio_gwu_0075A_16631.pdf | 2024-01-11 | Open Access |
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