Imagine blowing through a straw into a nearly empty glass–we probably all did this as children and sent water, milk, and soda flying everywhere! In essence, this video shows that same act, but filmed by a high-speed camera. The “straw” blows a steady stream of helium into a shallow pool of silicone oil and slowly moves so that the angle the straw makes with the pool changes. As the angle changes, different regimes are visible. First waves appear on the surface of the pool, then a bulge forms, which develops into a droplet stream, then on into the chaos of bubbles and jets. It’s good I couldn’t see this in slow motion as a child or I would have never used my straw for drinking!
Tag: droplets
Dancing Droplets
When a droplet falls onto a larger pool of the same liquid, it briefly sits on a layer of air that prevents coalescence. When that air drains away, the coalescence cascade–in which the droplet breaks into progressively smaller droplets until fully absorbed–begins. But if you vibrate the pool of liquid, the droplet bounces, effectively injecting more air between it and the pool. This prevents coalescence. What’s really neat here is that the researchers demonstrate this effect with arrays of droplets dancing in formation.
Geometrical Droplet Splashes
Sadly, this video shows no droplet impacts on a heart-shaped post, but maybe you can imagine what it would look like after seeing other geometrical shapes. Happy Valentine’s Day, guys!
High-Speed Leidenfrost Levitation
The Leidenfrost effect occurs when a liquid encounters a surface with a temperature much higher than its boiling point. Some of the liquid is instantly vaporized and then a droplet will skate across the surface on that vapor. This video shows the process at 3000 frames per second.
Levitating Liquid Oxygen
The Leidenfrost effect occurs between a fluid and a solid of vastly different temperatures. In the case of liquid oxygen, a thin layer of the oxygen vaporizes on contact with the room temperature solid, leaving a droplet of liquid oxygen to float along on its own vapor. Oxygen droplets are paramagnetic, meaning that they are susceptible to magnetic fields; in this video, scientists demonstrate how magnets can affect the motion of these droplets.
Droplet Impact in 3D
This stereo photo of a droplet by John Hart shows the formation of a crown and droplet breakup. It’s possible to see the picture in 3D by crossing one’s eyes. #
Steering Water Droplets
At the microscale, fluid behavior can be quite different than what we witness in everyday life. Mechanisms that have little effect on the macroscale suddenly become extremely important in a channel only a few hundred microns wide. Here, water droplets in oil are steered and controlled using lasers.
Water Drops at 10,000 FPS
We’ve seen water droplets join a larger pool at 2,000 frames per second, but what about 10,000 frames per second? (via Gizmodo)
Crown Breakup
When a droplet falls into a pool of similar fluid, one often observes a crown-like impact effect. This student video shows high-speed footage of different fluids crowning and explores the effects of surface tension on crown breakup.
Superfluid Dripping
This high-speed video shows superfluid helium dripping and breaking up. Although superfluid has no viscosity, this does not prevent the Plateau-Rayleigh instability from breaking the helium into droplets once the mass of the liquid is too great for surface tension to contain.
