Search results for: “lift”

Inside Hail Formation
Conventional wisdom suggests that hailstones form over the course of repeated trips up and down through a storm, but a new study suggests that formation method is less common than assumed. Researchers studied the isotope signatures in the layers of 27 hailstones to work out each stone’s formation history. They found that most hailstones (N = 16) grew without any reversal in direction. Another 7 only saw a single period when upwinds lifted them, and only 1 of the hailstones had cycled down-and-up more than once. They did find, however, that hailstones larger than 25mm (1 inch) in diameter had at least one period of growth during lifting.
So smaller hailstones likely don’t cycle up and down in a storm, but the largest (and most destructive) hailstones will climb at least once before their final descent. (Image credit: D. Trinks; research credit: X. Lin et al.; via Gizmodo)
Fediverse Reactions
May 13, 2025
Charged Drops Don’t Splash
When a droplet falls on a surface, it spreads itself horizontally into a thin lamella. Sometimes — depending on factors like viscosity, impact speed, and air pressure — that drop splashes, breaking up along its edge into myriad smaller droplets. But a new study finds that a small electrical charge is enough to suppress a drop’s splash, as seen below.
The drop’s electrical charge builds up along the drop’s surface, providing an attraction that acts somewhat like surface tension. As a result, charged drops don’t lift off the surface as much and they spread less overall; both factors inhibit splashing.* The effect could increase our control of droplets in ink jet printing, allowing for higher resolution printing. (Image and research credit: F. Yu et al.; via APS News)
*Note that this only works for non-conductive surfaces. If the surface is electrically conductive, the charge simply dissipates, allowing the splash to occur as normal.
Fediverse Reactions
May 8, 2025
Quietening Drones
A drone’s noisiness is one of its major downfalls. Standard drones are obnoxiously loud and disruptive for both humans and animals, one reason that they’re not allowed in many places. This flow visualization, courtesy of the Slow Mo Guys, helps show why. The image above shows a standard off-the-shelf drone rotor. As each blade passes through the smoke, it sheds a wingtip vortex. (Note that these vortices are constantly coming off the blade, but we only see them where they intersect with the smoke.) As the blades go by, a constant stream of regularly-spaced vortices marches downstream of the rotor. This regular spacing creates the dominant acoustic frequency that we hear from the drone.
Animation of wingtip vortices coming off a drone rotor with blades of different lengths. This causes interactions between the vortices, which helps disrupt the drone’s noise.
To counter that, the company Wing uses a rotor with blades of different lengths (bottom image). This staggers the location of the shed vortices and causes some later vortices to spin up with their downstream neighbor. These interactions break up that regular spacing that generates the drone’s dominant acoustic frequency. Overall, that makes the drone sound quieter, likely without a large impact to the amount of lift it creates. (Image credit: The Slow Mo Guys)
Fediverse Reactions
April 30, 2025
“My Own Galaxy”
Fungal spores sketch out minute air currents in this shortlisted photograph by Avilash Ghosh. The moth atop a mushroom appears to admire the celestial view. In the largely still air near the forest floor, mushrooms use evaporation and buoyancy to generate air flows capable of lifting their spores high enough to catch a stray breeze. (Image credit: A. Ghosh/CUPOTY; via Colossal)
Fediverse Reactions
February 14, 2025
When Fires Make Rain
The intense heat from wildfires fuels updrafts, lifting smoke and vapor into the atmosphere. As the plume rises, water vapor cools and condenses around particles (including ash particles) to form cloud droplets. Eventually, that creates the billowing clouds we see atop the smoke. These pyrocumulus clouds, like this one over California’s Line fire in early September 2024, can develop further into full thunderstorms, known in this case as pyrocumulonimbus. The storm from this cloud included rain, strong winds, lightning, and hail. Unfortunately, storms like these can generate thousands of lightning strikes, feeding into the wildfire rather than countering it. (Image credit: L. Dauphin; via NASA Earth Observatory)
October 16, 2024
Billowing Ouzo
Pour the Greek liquor ouzo into water, and your glass will billow with a milky, white cloud, formed from tiny oil droplets. The drink’s unusual dynamics come from the interactions of three ingredients: water, oil, and ethanol. Ethanol is able to dissolve in both water and oil, but water and oil themselves do not mix.
In this video, researchers explore the turbulent effects of pouring ouzo into water. In particular, pouring from the top creates a fountain-like effect, due to a tug-of-war between the ouzo’s momentum and its buoyancy. Momentum wants the ouzo to push down into the water, and buoyancy tries to lift it back up. For an extra neat effect, they also show what happens when the ouzo is confined to a 2D plane and what happens when momentum and buoyancy act together instead of oppositely. (Image and video credit: Y. Lee et al.)
Fediverse Reactions
October 2, 2024
The Art of French Drains
Civil engineers face a constant challenge trying to protect their structures from water — both above and below the ground. Subsurface water can build up enough pressure to lift and damage structures, so engineers use subsurface infrastructure — like French drains — to control the water underground. Despite the name (and my title pun), French drains have nothing to do with France. Instead, they are named for Henry French, an author who described their construction and use in the 19th century. These drains use a combination of rocks, mechanical filters, and perforated pipeline to guide subsurface water and drain it away from foundations. (Video and image credit: Practical Engineering)
September 11, 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: 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
Junggar Basin Aglow
The low sun angle in this astronaut photo of Junggar Basin shows off the wind- and water-carved landscape. Located in northwestern China, this region is covered in dune fields, appearing along the top and bottom of the image. The uplifted area in the top half of the image is separated by sedimentary layers that lie above the reddish stripe in the center of the photo. Look closely in this middle area, and you’ll find the meandering banks of an ephemeral stream. Then the landscape transitions back into sandy wind-shaped dunes. (Image credit: NASA; via NASA Earth Observatory)
July 24, 2024

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