Tag: olympics

Paris 2024: Diving
In competition diving, athletes chase a rip entry, the nearly splash-less dive that sounds like paper tearing. Part of a successful rip dive comes in the impact, where divers try to open a small air cavity with their hands that their entire body then enters. But the other key component happens below the surface, where divers bend at the hips once underwater. This maneuver enlarges the air cavity underwater and disrupts the formation of a jet that would typically shoot back upwards. Done properly, the result is an entry with little to no splash at the surface and a panel full of pleased judges. (Image credits: top – A. Pretty/Getty Images, other – E. Gregorio; research credit: E. Gregorio et al.; via Science News; submitted by Kam-Yung Soh)
Sequence of images showing a synthetic diver bending underwater to disrupt splash formation.
Related topics: Rip entry physics, how pelicans dive safely, and how boobies plunge dive
This post marks the end of our Olympic coverage for this year’s Games, but if you missed any previous entries, you can find them all here.
August 9, 2024
Paris 2024: Clearing the Air
A quartet of mushroom-shaped structures tower nearly 6 meters above the Olympic Village. Known as Aerophiltres, these devices filter particulates out of the air to provide cleaner air for the Village, despite its proximity to major roadways. There’s no need to change out the filters in the Aerophiltres, though, because they don’t have any. Instead, the devices ionize fine particles, encourage them to clump together, and then capture them on highly-charged metal plates. A fan near the base sucks polluted air in through the top and expels clean air at the ground level. According to the engineers, the system is capable of removing 95% of particulates and producing nine Olympic-sized swimming pools’ worth of clean air each hour. Compared to traditional systems — which require lots of power to suck air through filters that get progressively more clogged — the Aerophiltres are energy efficient, highly effective, and easy to maintain. (Image credit: SOLIDEO/C. Badet; via DirectIndustry)
Related topics: How manta rays filter without clogging, making artificial snow, and building whitewater rafting courses
Catch our past and ongoing Olympic coverage here.
August 8, 2024
Paris 2024: Gunwale Bobbing
In the Olympics, you won’t see anyone win a rowing event without a paddle, but it turns out that you don’t really need one for a canoe or paddleboard. How can you get around when you’ve lost your paddle? You stand up on one end and start bobbing. This is known as gunwale (pronounced gunnel) bobbing, and it’s pretty impressively effective! With optimal parameters, scientists found that a canoe could move about 1 m/s with the technique.
As the bobber pushes, it generates an asymmetric wave field on the water surface. The canoe or paddleboard then essentially surfs those waves, turning the vertical displacement into a horizontal thrust. The researchers expect that the effect matters for competitive rowing, too, where the athletes’ rowing motions cause some vertical displacement. Clearly, the biggest effect comes from the oars themselves, but optimal bobbing could provide enough of an edge to ensure the gold. (Image credit: top – R. Chisu; others – G. Benham et al.; research credit: G. Benham et al.; via APS Physics; submitted by Kam-Yung Soh)
Related topics: Optimizing oar length, vorticity around an oar, and a vibration-propelled biorobot
See more of our past and ongoing Olympic coverage here.
August 7, 2024
Paris 2024: Tennis Racket Physics
Like many sports that feature balls, spin plays a big role in tennis. By imparting a topspin or backspin to a tennis ball, players can alter the ball’s trajectory after a bounce and, using the Magnus effect to alter lift around the ball, change how it travels through the air. For example, a ball hit with backspin can dive just after the net, forcing an opponent to scramble after it. How much spin a player can impart depends on the speed of the racket’s head. Competitive rackets are carefully engineered — in terms of weight, string tension, and frame stiffness — to translate the kinetic energy of a player’s swing into the ball. But aerodynamics also play a role: new rackets designed to minimize drag hit the market 15-20 years ago, promising drag reductions up to 24% compared to previous rackets. That gives a player more swing speed and higher spins at a lower energy cost. (Image credit: C. Costello)
Related topics: The Magnus effect in table tennis and in golf; the reverse Magnus effect
Check out more of our ongoing and past Olympic coverage here.
August 6, 2024
Paris 2024: Beach Versus Indoor Volleyballs
Some of the differences between beach volleyball and indoor volleyball are obvious, like the number of players allowed — two versus six — and the courts — a smaller sand court versus a bigger indoor court. But there are subtle and significant differences in the balls themselves. Both beach and indoor volleyballs used for competition are required to weigh between 260 and 280 grams, but the expected diameter of the balls differs by about 1 centimeter, with beach volleyballs coming out slightly larger. The balls differ in their surface roughness, too, with indoor models being smoother, even before in-game wear.
Although these differences seem minor, they can make a significant impact in the game. Volleyball regulations don’t specify a ball’s expected surface roughness or how many panels they should be made with. As in football, these seemingly cosmetic changes can strongly affect airflow around the ball and change its trajectory. Regulations require that all balls used in a given match be uniform, but that still requires athletes to potentially adjust to the behavior of a new ball at each competition. (Image credits: I. Garifullin, C. Chaurasia, C. Oskay, and M. Teirlinck)
Related topics: How smoothness and panel design affect a football, volleyball aerodynamics, and vortex generators on cycling skinsuits
For more ongoing and past Olympic coverage, click here.
August 5, 2024
Paris 2024: Cycling in Crosswinds
Wind plays a major role in cycling, since aerodynamic drag is the greatest force hampering a cyclist. In road racing, both individual cyclists and teams use tactics that vary based on the wind speed and direction. Crosswinds — when the apparent wind comes from the side in the cyclist’s point of view — are some of the toughest conditions to deal with. In races, groups will often form echelons to minimize the group’s overall effort in a crosswind. Alternatively, racers looking to tire their competitors out will position themselves on the road so that the rider behind them gets little to no shelter from the wind; this is known as guttering an opponent.
In this study, researchers put a lone cyclist in a wind tunnel and measured the effects of crosswind from a pure headwind to a pure tailwind and every possible angle in between. From that variation, they were able to mathematically model the aerodynamic effects of crosswind on a cyclist from every angle. With rolling resistance (a cyclist’s second largest opposing force) included, they found relatively few conditions where a crosswind actually helped a cyclist. Most of the time — as any cyclist can tell you — hiding from the wind is beneficial. (Image credit: J. Dylag; research credit: C. Clanet et al.)
Related topics: The physics of the Tour de France, how the peloton protects riders aerodynamically, track cycling physics, and a look inside wind tunnel testing bikes and cyclists
Catch all of our ongoing Olympics coverage here.
August 2, 2024
Paris 2024: Coordinating the Front-Crawl
Of all the swimming strokes humans have invented, none is faster or more efficient than the front-crawl. That’s why all competitors use it in freestyle events, and why it’s the only stroke that appears in races longer than 200 meters. But elite swimmers don’t perform the front-crawl the same way in a sprint as they do in a longer race. Instead, researchers found that swimmers use three different regimes of arm coordination.
For long-distance races, elite swimmers adopt a stroke that has only one arm in the water at a time. Each stroke is followed by a glide phase with one arm stretched in front of them. Researchers compared this to the burst-and-coast method that fish use to minimize the energy they use. As a swimmer’s speed increases, they shorten the glide phase and begin to maximize the force produced with each propulsive stroke.
In the third regime — the fastest one used by elite sprinters — the strokes of a swimmer’s arms are superposed, with both arms engaged in propulsion at the same time during parts of the cycle. This mode maximizes propulsive force but requires a lot of energy, so swimmers can only sustain it for a short while.
Since researchers built their observations into a physical model that explains how and why elite swimmers do this, the model can actually be used to advise individual swimmers on how they can adapt their stroke based on their size, desired speed, and other physical characteristics. (Image credit: J. Chng; research credit: R. Carmigniani et al.)
Related topics: More on swimming physics including why swimmers are faster underwater and how to design faster pools.
Find all of our current and past Olympics coverage here.
August 1, 2024
Paris 2024: Bouncing and Spinning
Spin, or the lack thereof, plays a major role in many sports — including tennis, golf, football, baseball, volleyball, and table tennis — because it affects whether flow stays attached around a ball, as well as how much lift or side force a ball gets. A ball’s spin doesn’t stay constant, however. During flight, a ball’s spin decays at a rate proportional to its initial spin and velocity. Researchers have found that a ball’s moment of inertia, flow regime, and surface roughness all affect that decay, but which factor is the most significant varies by ball and by sport.
Whether a ball bounces while spinning also matters. For compliant balls on a non-compliant surface — think tennis balls on a court — a bounce can actually change how much a ball spins. During impact, a tennis ball can: slide, decreasing its tangential velocity while increasing its topspin; roll, where the ball’s tangential velocity matches the tangential velocity of the surface; or over-spin, where the ball spins faster than it rolls. For a given impact angle and velocity, researchers found that stiffer and/or lighter balls were more likely to over-spin. Within tennis’s allowable range of ball stiffness and mass, manufacturers could create tennis balls that over-spin far more than conventional ones, creating another opportunity for deceptive tactics in the sport. (Image credit: J. Calabrese; research credit: T. Allen et al.)
Related topics: How flow separates from a surface, and why turbulence is sometimes preferable
Find all of our Olympics coverage — past and ongoing — here and every sports post here.
July 31, 2024
Paris 2024: Triathlon Swimming
Unlike the swimming competition, Olympic triathletes complete their swim legs in open waters. There are no lane dividers and no rules against drafting off a fellow athlete. Curious to see how draft positioning could affect swimmers, researchers experimented with swimmer-shaped models in a water channel and a numerical simulation. They found that the most advantageous position is directly behind a lead swimmer, where the follower could enjoy a 40% reduction in drag. Another good position is near the leader’s hip, where waves off the leader provide a 30% reduction in drag.
The worst place to swim, interestingly, is immediately side-by-side. With both swimmers neck-in-neck, drag is maximized, and each swimmer feels more drag than they would swimming by themselves! (Image credit: J. Romero; research credit: B. Bolan et al.)
Related topics: Drafting in each triathlon stage and drafting effects in nordic skiing
Join us all this week and next for more Olympics-themed stories.
July 30, 2024
Paris 2024: Swimsuit Tech
The aughts were an exciting time to watch competitive swimming. Records were falling left and right, especially in 2008 and 2009. The first wave of improvements came around 2000, with the introduction of full-body swimwear. According to one analysis, men’s freestyle swimming performances improved by about 1% with that change. The next big leap came in 2008 when companies introduced polyurethane panels into the suits (most famously the LZR Razer suits pictured above) causing an additional 1.5-3.5% performance improvement. The panels were stiff, reducing the swimmer’s cross-sectional area and thereby reducing drag. Their effect was greatest in sprint events; long-distance swimmers saw fewer improvements, possibly because turning in the stiffer suits was tiring.
The biggest leap came in 2009 with all polyurethane full-body swimsuits, which streamlined swimmers and gave them skin friction improvements that let them slip through the water more easily. Freestyle swimmers with those suits were showing a full 5.5% performance improvement on top of the 2000-era full-body suits.
With so many records falling in 2008 and 2009 — largely to swimmers wearing the expensive new suits that some teams could not afford — swimming’s federation chose to ban the new technology, causing an immediate drop in performances to pre-polyurethane levels. Although sprint performances will likely improve little by little each year, no one is likely to break the sprint records of 2008-2009 in the next decade — not unless the federation establishes a “new rules” record the way officials did with the javelin after a major rule change. (Image credit: Getty Images; research credit: L. Foster et al.)
Today kicks off our fluids-themed Olympics coverage. Stay tuned for more sports this week and next week. If that’s not enough sports physics for you, check out what we wrote in previous years.
July 29, 2024