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The Herald Scotland
22-05-2025
- Science
- The Herald Scotland
The best way to make a huge splash in the pool (it's very hard to do)
Now, scientists at the Georgia Institute of Technology have worked out the mechanics of exactly what these divers are doing to create their massive splashes - and it's a far cry from the simplicity of a belly buster. "It's very difficult to master, it can be quite dangerous, and it requires millisecond control," said Pankaj Rohilla, a postdoctoral researcher and co-author on the paper "Mastering the Manu--how humans create large splashes," published on May 19. The Georgia Tech team of fluid dynamics and biomechanics experts spent months working on the problem. Learning the mechanics involved analyzing more than 75 videos of people doing manu jumps, then taking lab members to Georgia Tech's pool to do more than 50 trial jumps, all filmed in high definition to capture exactly what their bodies were doing at each millisecond. Finally, researcher and co-author Daehyun Choi built a "Manubot," a hand-sized robot that could mimic a diver's body movements during a manu jump to test what exact angle was best to create the biggest possible movement of water. Making the biggest splash possible What Maori jumpers have perfected turns out to involve specific movements all done within as little as 0.14 seconds of each other -- and the exact opposite of the techniques taught to traditional divers, as seen every four years during the Olympics. "It's all about making a V-shape with your body during water entry and then a specific set of underwater body dynamics," said Rohilla. Specifically, the best manu jumpers form a perfect 45-degree V with their bodies in the air. Then, as soon as they touch the water's surface, the diver rolls back and kicks to straighten their body out. This expands the air cavity created when their body enters the water. The height of the splash corresponds to the size of that cavity. The time of cavity collapse is known as the "pinch-off time." Gravitational forces push the water back in the vertical direction, generating an upward jet of water. "It's basically about how much energy you're trapping underwater," said Rohilla. Technically, the initial splash created by the diver's body entering the water is called the crown splash, while the second, caused by the collapsing air cavity, is called a Worthington jet. It requires extreme body control and split-second timing. The V-shape of the body has to be a 45-degree angle to create the fastest and highest Worthington jet, while ensuring the diver's safety. The roll back and kick motion must occur within 0.14 to 0.15 seconds of entering the water when the diver is jumping from 3 meters, said Rohilla. That's about 10 feet high. The higher the jump, the shorter the time the diver has to perform the roll back and kick. "It looks easy but it's actually very challenging," he said. Manu diving can hurt The researchers caution that the manu maneuver is not only difficult but can be risky and painful. "The higher you jump, the less reaction time you have. So it can be quite dangerous," said Rohilla. Especially if you miss the landing shape of 45 degrees, the water can slap the diver's back with a lot of force. "That hurt a few of our teammates. It was very painful," Rohilla said. "You could even hurt your spine, so it can be a risky sport." Manu diving has been banned in some pools in New Zealand, including one area where a child was injured. A Maori cultural sport The sport back at least several decades and has become an important cultural tradition in New Zealand. The name most likely comes from the Maori word "manu" which means bird, though some suggest it's a shortened form of Mangere, a suburb of Auckland where the sport is popular. It's gone from something people did for fun to showing off their prowess as a competitive sport. In 2024, the first Manu World Championships were held in New Zealand's capital, Wellington. Other competitions appeared to have been held dating back to at least 2011. In Wellington this year, more than $23,000 in prize money is on the line. Jump heights range from three feet above the water for children to as high as 16 feet for adults. Divers can compete in the traditional manu style of the V-Bomb, but new styles have also been introduced, including The Gorilla, the Cannonball, and The Coffin. The competition uses high-tech cameras to calculate the splash height of each diver to ensure fair scoring. 'Thousands and thousands of hours of practice' The fun of manu diving is making a huge splash, something people love given the quantity of splashes observed wherever children play in pools. It's also the exact opposite of the clean, minimal splash demanded in competitive diving, where scoring depends, in part, on producing the smallest possible splash as the diver plunges into the water. "We call it 'ripping,'" said Phil Tonne, a dive coach at the University of California, Davis. "The least amount of splash correlates to the highest scores." Making no splash is as hard as making a big splash. "You want to be as streamlined as you can possibly get," Tonne said. "It takes thousands and thousands of hours of practice."
USA Today
21-05-2025
- Science
- USA Today
Scientists report the best way to make a huge splash when jumping in a pool
Scientists report the best way to make a huge splash when jumping in a pool A unique and fiendishly difficult type of diving has been perfected by the Māori of New Zealand. It can shoot out 32-foot water jets. Show Caption Hide Caption At US Olympic diving trials, Olympians will pass down their rings When a diver qualifies for the Paris Games at the U.S. diving trials, former Olympians will pass down a token to the next generation. Sure, there's the bellyflop. The cannonball. The bomb. But for the biggest pool splash of all, nothing beats "popping a Manu," a unique and fiendishly difficult type of diving perfected by the Māori of New Zealand that can shoot up 32-foot water jets. The decades-old cultural tradition is so popular that there's an annual world championship held in Auckland with cash prizes, the most recent of several such events over the past two decades. Now, scientists at the Georgia Institute of Technology have worked out the mechanics of exactly what these divers are doing to create their massive splashes – and it's a far cry from the simplicity of a belly buster. "It's very difficult to master, it can be quite dangerous, and it requires millisecond control," said Pankaj Rohilla, a postdoctoral researcher and co-author on the paper "Mastering the Manu—how humans create large splashes," published on May 19. The Georgia Tech team of fluid dynamics and biomechanics experts spent months working on the problem. Learning the mechanics involved analyzing more than 75 videos of people doing manu jumps, then taking lab members to Georgia Tech's pool to do more than 50 trial jumps, all filmed in high definition to capture exactly what their bodies were doing at each millisecond. Finally, researcher and co-author Daehyun Choi built a "Manubot," a hand-sized robot that could mimic a diver's body movements during a manu jump to test what exact angle was best to create the biggest possible movement of water. Making the biggest splash possible What Māori jumpers have perfected turns out to involve specific movements all done within as little as 0.14 seconds of each other — and the exact opposite of the techniques taught to traditional divers, as seen every four years during the Olympics. "It's all about making a V-shape with your body during water entry and then a specific set of underwater body dynamics," said Rohilla. Specifically, the best manu jumpers form a perfect 45-degree V with their bodies in the air. Then, as soon as they touch the water's surface, the diver rolls back and kicks to straighten their body out. This expands the air cavity created when their body enters the water. The height of the splash corresponds to the size of that cavity. The time of cavity collapse is known as the "pinch-off time." Gravitational forces push the water back in the vertical direction, generating an upward jet of water. "It's basically about how much energy you're trapping underwater," said Rohilla. Technically, the initial splash created by the diver's body entering the water is called the crown splash, while the second, caused by the collapsing air cavity, is called a Worthington jet. It requires extreme body control and split-second timing. The V-shape of the body has to be a 45-degree angle to create the fastest and highest Worthington jet, while ensuring the diver's safety. The roll back and kick motion must occur within 0.14 to 0.15 seconds of entering the water when the diver is jumping from 3 meters, said Rohilla. That's about 10 feet high. The higher the jump, the shorter the time the diver has to perform the roll back and kick. "It looks easy but it's actually very challenging," he said. Manu diving can hurt The researchers caution that the manu maneuver is not only difficult but can be risky and painful. "The higher you jump, the less reaction time you have. So it can be quite dangerous," said Rohilla. Especially if you miss the landing shape of 45 degrees, the water can slap the diver's back with a lot of force. "That hurt a few of our teammates. It was very painful," Rohilla said. "You could even hurt your spine, so it can be a risky sport." Manu diving has been banned in some pools in New Zealand, including one area where a child was injured. A Māori cultural sport The sport back at least several decades and has become an important cultural tradition in New Zealand. The name most likely comes from the Māori word "manu" which means bird, though some suggest it's a shortened form of Māngere, a suburb of Auckland where the sport is popular. It's gone from something people did for fun to showing off their prowess as a competitive sport. In 2024, the first Manu World Championships were held in New Zealand's capital, Wellington. Other competitions appeared to have been held dating back to at least 2011. In Wellington this year, more than $23,000 in prize money is on the line. Jump heights range from three feet above the water for children to as high as 16 feet for adults. Divers can compete in the traditional manu style of the V-Bomb, but new styles have also been introduced, including The Gorilla, the Cannonball, and The Coffin. The competition uses high-tech cameras to calculate the splash height of each diver to ensure fair scoring. 'Thousands and thousands of hours of practice' The fun of manu diving is making a huge splash, something people love given the quantity of splashes observed wherever children play in pools. It's also the exact opposite of the clean, minimal splash demanded in competitive diving, where scoring depends, in part, on producing the smallest possible splash as the diver plunges into the water. "We call it 'ripping,'" said Phil Tonne, a dive coach at the University of California, Davis. "The least amount of splash correlates to the highest scores." Making no splash is as hard as making a big splash. "You want to be as streamlined as you can possibly get," Tonne said. "It takes thousands and thousands of hours of practice."
RNZ News
17-05-2025
- Science
- RNZ News
‘Manu jumping': The physics behind making humongous splashes in the pool
By Pankaj Rohilla and Daehyun Choi* of Supreme champion Kree Smith, of Northland's Wainui Valley, hits the water at Russell's Manu Masters. Photo: RNZ/Peter de Graaf Whether diving off docks, cannonballing into lakes or leaping off the high board, there's nothing quite like the joy of jumping into water. Olympic divers turned this natural act into a sophisticated science, with the goal of making a splash as small as possible. But another sport looks for just the opposite: the extreme maximum splash, one as high, wide and loud as possible. Welcome to the world of " manu jumping ". Although not a familiar term in the United States, manu jumping is beloved throughout New Zealand. The sport originated in Māori communities, where popping a manu is a way of life. Manu jumpers are known for leaping from bridges, wharves and diving platforms to make the giant splashes. The sport is playful yet competitive. At the Z Manu World Champs , you win based on the height and width of your splash. The current record: a splash more than 10 metres high . The concept sounds simple, but like Olympic diving, it turns out there's a science to manu jumping. As fluid dynamicists , we study the way living organisms interact with fluids - for instance, how flamingos feed with their heads underwater, or how insects walk on water. So when we stumbled upon viral videos of manu jumping on TikTok and YouTube, our curiosity was triggered. We launched a scientific investigation into the art of making a splash. Our research was more than just fun and games. Optimising how bodies enter fluids - whether those bodies are human, animal or mechanical - is an indispensable branch of science. Understanding the physics of water entry has implications for naval engineering, biomechanics and robotics. We discovered that creating the perfect manu splash isn't just about jumping into the water. Instead, it's about mastering aerial maneuvers, timing underwater movements and knowing exactly how to hit the surface. The microsecond the manu jumper hits the water is critical. Two splashes actually occur: The first, the crown splash, forms as the body breaks the surface. The next, the Worthington splash, is responsible for the powerful burst of water that shoots high into the air. Manu jumping is all about triggering and maximising the Worthington splash. So we analysed 75 YouTube videos of manu jumps. First, we noticed the technique: Jumpers land glutes first, with legs and torso scrunched up in a V-shaped posture. But the moment they go underwater, the divers roll back and kick out to straighten their bodies. This expands the air cavity, the space of air created in the water by the jump; then the cavity collapses, detaching itself from the body. This period of detachment is known as "pinch-off time" - when the collapse sends a jet of water shooting upward. All of this happens within a fraction of a second. We found that jumpers entered the water at a median V-angle of about 46 degrees. Intrigued, we recreated these movements in a lab aquarium, using 3D-printed, V-shaped projectiles to test different V-angles. The result? A 45-degree angle produced the fastest, tallest splashes, virtually matching what we observed in the human jumpers. V-angles greater than 45 degrees increased the risk of injury from landing flat on the back. We found it interesting that the jumpers very nearly hit the optimal angle largely through what appeared to be intuition and trial and error. Digging deeper, we then built Manubot, a robot that mimics human body movements during manu jumps. It's able to switch from a V-shape to a straight posture underwater. This is how we learned the optimal timing to maximise splash size. For instance, for someone who's 5ft 7in (170cm) and jumping from 1m, opening their body within 0.26 to 0.30 seconds of hitting the water resulted in the biggest splash. Open too soon or too late, and splash size is compromised. One caveat: Humans are far more complex than any 3D-printed projectile or a Manubot. Factors such as weight distribution, flexibility and anatomical shape add nuance that our models can't yet replicate. For now, though, our findings highlight a simple truth: Creating the perfect manu splash isn't the result of luck. Instead, it relies on a carefully tuned symphony of aerial and underwater manoeuvres. So the next time you see someone spray everyone in the pool with a gigantic jump, remember - there's a beautiful science behind the splash. * Pankaj Rohilla and Daehyun Choi are Postdoctoral Fellows at Georgia Institute of Technology. - This story was originally published on The Conversation .
