The act of performing a belly flop into a swimming pool may seem like a simple and fun activity, but the physics behind it are more complex than one might expect. Daniel Harris, an assistant professor in Brown University’s School of Engineering, has delved into understanding the forces and impact involved in belly flopping. Not only does this research provide insights into the painful experience of a belly flop, but it also has important implications in naval and marine engineering, where structures must withstand high-impact air-to-water slamming forces.
Harris, along with graduate student John Antolik and a team of researchers from the Naval Undersea Warfare Center and Brigham Young University, conducted a study using a blunt cylinder with a unique twist. They attached a flexible “nose” to the cylinder, allowing it to deform upon impact, simulating the conditions of a belly flop. This experiment aimed to explore the changes in physics and forces experienced when the impacting object is flexible.
Contrary to conventional thinking, the researchers discovered that a more flexible system does not always soften the impact of a belly flop. In fact, in some cases, a flexible structure can increase the maximum impact force on the body compared to a rigid structure. To understand this phenomenon, extensive experiments and a theoretical model were developed.
The researchers found that the key to reducing the impact force lies in the flexibility of the springs attached to the cylinder. The springs, acting akin to a car’s suspension, are intended to distribute the impact load over a longer period. However, if the springs are too stiff or not timed correctly, they can exacerbate the force experienced by the body. The structure’s own vibrations during the impact further compound the slamming force.
Inspired by diving birds, the researchers are now exploring next steps in their research line. Biological studies of these birds have revealed specific maneuvers that help them enter the water without experiencing high forces. By studying and understanding these natural mechanisms, the researchers hope to uncover additional strategies for mitigating the impact of belly flops and similar high-impact air-to-water transitions.
While belly flopping may be a source of entertainment or pain for many, the research conducted by Harris and his team has far-reaching implications. Naval and marine engineering structures often encounter high-impact air-to-water slamming forces, and understanding the mechanics involved is crucial for designing resilient structures. By incorporating flexible systems and developing strategies to absorb and distribute the impact load, engineers can enhance the durability and safety of these structures.
The study of belly flops goes beyond the realm of poolside trivia. It provides valuable insights into the physics and forces that occur during high-impact air-to-water transitions. Through experiments and theoretical models, researchers have discovered the importance of flexibility and proper timing in reducing impact forces. As they look to nature for inspiration, the aim is to apply these findings to naval and marine engineering, promoting the development of structures that can withstand extreme forces and contribute to safer and more efficient maritime operations.