Although the mechanics of jumping on water dominated by surface tension are well established, the understanding of water jumping dominated by drag force, as observed in organisms like fishing spiders, remains incomplete despite its potential to achieve high jumping velocity. Here, we demonstrate that simple elastic hoops can achieve drag-dominated jump on water, and use this model system to construct a fundamental framework to theoretically analyze jump dynamics propelled by form drag. In addition to numerically solving the hoop trajectory while interacting with water, we show that the take-off velocity scaled by the hoop's free vibration velocity depends solely on the solid-fluid density ratio. A comparison with hoop jumps on solid ground reveals that the hoop jumps on water are delayed with a lower jumping efficiency. This work can not only contribute to the development of efficient and easily constructible biomimetic robots but also provide a foundation for understanding the optimal design principles and evolutionary pressures that shape biological jumpers.

• Received 15 June 2023
• Accepted 28 August 2023

DOI:https://doi.org/10.1103/PhysRevFluids.8.100503