Mastering the Manu - How humans create large splashes

Manu jumping, a popular water diving style amongst Maori people in New Zealand, focuses on creating large splashes. Divers perform aerial maneuvers such as the "utkatasana" pose, entering the water in a V-shape, and executing underwater maneuvers to maximize the splash size. Our study explores the underlying fluid dynamics of Manu jumping and demonstrates how two key parameters, the V-angle and the timing of body opening, can maximize the Worthington jet formation. To accurately replicate human manu jumping, we studied water entry of both passive solid objects with varying V angles and an active body opening robot (Manubot). The analysis revealed that a 45-degree V angle is optimal for maximizing Worthington jet formation, consistent with human diving data. This angle balances a large cavity size and a deep pinch-off depth. The body opening within a timing window of t?r = 1.1-1.5 synchronizes the robot's potential energies to be timely transferred to the cavity formation, producing the strongest and most vertical, i.e., ideal, Worthington jets. Based on our experimental findings, we propose optimal parameters for generating the largest Manu splashes. These insights offer engineering perspectives on how to modulate underwater cavity dynamics using both passive and active body formations.