Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
From Dripping to Beading
When water drips, it quickly breaks up into a string of smaller droplets due to a surface-tension-driven instability called the Plateau-Rayleigh instability. But adding just a tiny bit of polymer to the fluid changes the behavior entirely. Instead of breaking into droplets, a narrow filament dotted with tiny satellite droplets forms between the larger drops.…
Trampolining Droplet
Imagine a droplet sitting on a rigid surface spontaneously bouncing up and then continuing to bounce higher after each impact, as if it were on a trampoline. It sounds impossible, but it’s not. There are two key features to making such a trampolining droplet–one is a superhydrophobic surface covered in an array of tiny micropillars…
Science Hackathon
Just a heads-up that I’ll be at Brown University tomorrow giving a talk and then helping out with a science visualization hackathon. I’m super excited for the opportunity to have some hands-on flow visualization fun with folks! The lecture is public, but I think only Brown students can register for the workshop.
Ignition
Shown here are the first instants after a bubble full of methane gas is ignited via laser. Using the schlieren optical method and a high-speed camera, scientists recorded the deflagration at 10,000 frames per second. Because schlieren imaging is very sensitive to small changes in density, we see not only the expanding flame front as…
The Droplet Slide
One of the joys of science is the sense of discovery that can come even from looking at something seemingly simple. Take, for example, a water droplet sitting on a plate. If you slowly tilt the plate, the droplet’s shape will shift until a critical angle where it starts sliding down the plate. But what…
Viscous Fingers
Take a viscous fluid, like laundry detergent, and sandwich it between two plates of glass. Fluid dynamicists call this set-up a Hele-Shaw cell. If you then inject a less viscous fluid, like air, between the plates–or if you try to pry them apart–you’ll see a distinctive pattern of dendritic fingers form. This viscous fingering, also…
Cream in Coffee
Pouring cream in coffee produces some of the most mesmerizing displays of fluid dynamics. The density difference between the two fluids sets up Rayleigh-Taylor instabilities that mushroom out and help create the turbulence that eventually mixes the drink. You can learn more about Rayleigh-Taylor instabilities in this FYFD video, and, if you need more awesome…
Waves Over the Rockies
These spectacular wave-like clouds are the result of the Kelvin-Helmholtz instability. When two layers of air move past one another at different velocities, an unstable shear layer forms at their interface. Disturbances in this shear layer grow exponentially, creating these short-lived overturning waves that quickly turn turbulent. The strong resemblance of these clouds to breaking…
Deforming Soap Films
It’s the time of year when new Gallery of Fluid Motion videos start popping up online. We’ve already featured several and no doubt there will be more to come. Today’s post is a submission from Saad Bhamla, who gave this introduction to the work: Soap bubbles occupy the rare position of delighting and fascinating both…
Re-Entry
Atmospheric re-entry subjects vehicles to extreme conditions. At high Mach numbers, the leading shock wave compresses the air so strongly that it reaches temperatures hotter than the surface of the sun. At these temperatures, oxygen and nitrogen molecules in the air dissociate, bathing a vehicle in a plasma of ionized gas molecules. Often these atoms…