How and why this takes place in fluid mechanics isnt simply crucial for establishing a prize-winning tummy flop for competitors, or dolling out pool-party trivia on why tummy flops harmed so much– the understanding is crucial to marine and marine engineering, which typically have structures that need to survive high-impact air-to-water slamming forces.” Most of the work thats been done in this space looks at stiff bodies knocking into the water, whose general shape does not truly alter or move in action to the impact,” Harris stated. “The questions that we start to get at are: What if the item thats affecting is versatile so that when it feels the force it can either alter shape or deform? Depending on the height from which the impactor is dropped and how stiff the springs are, the body will not just feel the impact from the slam but it will likewise feel the vibrations of the structure as it gets in the water, compounding the slamming force.
Researchers at Brown University established a belly flop-like water experiment using a blunt cylinder however adding an essential vibrating twist to it, which eventually led them to counterintuitive findings. Credit: Video offered by John Antolik and Daniel Harris
Experiments by a Brown-led research team examined stubborn belly flop mechanics and discovered unexpected insights about air-to-water impacts that could be beneficial for marine engineering applications.
Anyone whos ever done a stomach flop into a pool knows it ends with a blunt-sounding splat, a big splash and a searing red sting. What many people dont know is why.
Daniel Harris does. The assistant professor in Brown Universitys School of Engineering says the physics behind the phenomenon arent too complicated. What occurs– and what makes it so uncomfortable, he discusses– is that the forces from the water surface put up an intense resistance to the body unexpectedly going from air to water, which is often still.
What occurs– and what makes it so uncomfortable, he describes– is that the forces from the water surface area put up a strong resistance to the body suddenly going from air to water, which is often still.
” All of a sudden, the water needs to speed up to capture up to the speed of whats failing the air,” said Harris, who studies fluid mechanics. “When this occurs, that large reaction force is returned to whatevers doing the impacting, resulting in that signature slam.”
Belly-flop mechanics isnt simply crucial for establishing a prize-winning stomach flop for competitions, or dolling out pool-party trivia on why belly flops hurt so much– the understanding is crucial to naval and marine engineering.
Insights From Fluid Mechanics Research
How and why this takes place in fluid mechanics isnt just important for establishing a prize-winning tummy flop for competitors, or dolling out pool-party trivia on why stubborn belly flops harmed a lot– the understanding is crucial to marine and naval engineering, which typically have structures that need to survive high-impact air-to-water slamming forces. For that reason, the phenomenon has actually been studied thoroughly for the past century. A research study group led by Harris and Brown graduate student John Antolik discovered unique insights in a new study done in collaboration with scholars at the Naval Undersea Warfare Center in Newport and Brigham Young University.
For the Journal of Fluid Mechanics research study, the researchers set up a tummy flop-like water experiment utilizing a blunt cylinder however adding an essential vibrating twist to it, which ultimately led them to counterproductive findings.
Brown researchers set up a stomach flop-like water experiment utilizing a blunt cylinder but including an essential vibrating twist to it, which ultimately led them to counterproductive findings. Credit: Video supplied by John Antolik and Daniel Harris
” Most of the work thats been performed in this area takes a look at rigid bodies slamming into the water, whose general shape does not really move or alter in response to the impact,” Harris said. “The questions that we start to get at are: What if the object thats impacting is versatile so that once it feels the force it can either alter shape or deform? How does that modification the physics and after that, more significantly, the forces that are felt on these structures?”
To address that, the scientists attached a soft “nose” to the body of their cylinder, described as an impactor, with a system of versatile springs.
The concept, Antolik describes, is that the springs– which act in concept comparable to the suspension of an automobile– need to assist soften the effect by distributing the impact load over a longer duration. This strategy has been drifted as a possible option for decreasing sometimes disastrous slamming impacts in air-to-water shifts, but few experiments have ever looked carefully at the basic mechanics and physics involved.
For this experiment, the researchers dropped the cylinder consistently into still water and examined both the visual outcomes and information from sensing units embedded inside the cylinder.
This is where the unforeseen happened.
The results reveal that while the method can be efficient, remarkably, it does not constantly soften the impact. In truth, contrary to conventional thinking, often the more versatile system can increase the optimum effect force on the body as compared to a totally stiff structure.
This required the researchers to dig much deeper. Through substantial experiments and by developing a theoretical model, they discovered their response. Depending on the height from which the impactor is dropped and how stiff the springs are, the body will not just feel the impact from the slam however it will likewise feel the vibrations of the structure as it goes into the water, compounding the slamming force.
” The structure is vibrating backward and forward due to the violent impact, so we were getting readings from both the effect of hitting the fluid and an oscillation due to the fact that the structure is shaking itself,” Harris said. “If you dont time those best, you can basically make the circumstance worse.”
The scientists discovered the secret was the springs: they need to be soft enough to gently take in the effect without resulting in more fast vibrations that add to the overall force.
Operating in Browns Engineering Research Center, Antolik recorded the experiments utilizing high-speed electronic cameras and used an impact measurement tool called an accelerometer. “The entire back corner gets a little bit wet when Im doing the experiments,” he joked.
Practical Applications and Future Research
When it comes to swimmers seeking to lessen the discomfort from their next belly flop, the secret may be trying to cushion the impact of the slamming forces, perhaps with a padded wet-suit or some type of product or item with a spring to it.
” I expect the ethical of our story would be that the product must be picked sensibly so regarding not make the situation even worse,” Harris said.
The researchers are now taking a look at next steps in their research line, taking inspiration from diving birds.
” Biological research studies of these birds have actually revealed that they carry out certain maneuvers as they enter the water to improve the conditions so they dont experience such high forces,” Antolik said. “What were moving towards is trying to create what is basically a robotic impactor that can carry out some active maneuver during water entry to do the same for blunt items.”
Referral: “Slamming forces during water entry of a simple harmonic oscillator” by John T. Antolik, Jesse L. Belden, Nathan B. Speirs and Daniel M. Harris, 6 November 2023, Journal of Fluid Mechanics.DOI: 10.1017/ jfm.2023.820.
The study was supported by the Office of Naval Research and Naval Undersea Warfare Center.