Supercooling is the process of lowering a fluid’s temperature below its freezing point without the fluid becoming solid. Though this may sound bizarre, it’s an effect you can recreate easily in your refrigerator, as detailed in the video above. Supercooling shows up in nature as well, particularly with water droplets at high altitudes. If a plane flies through supercooled water droplets, it can create icing problems on the aircraft’s wings. Alternatively, flying through supercooled water vapor can cause a hole-punch cloud to form when the vapor flash-freezes into snow. (Video credit: SciShow)
Tag: fluid dynamics
Van Gogh and Turbulence
Turbulence is one of the great unsolved mysteries of classical mechanics. Many physicists and engineers have spent their careers trying to further our understanding of the subject and find the mathematical pattern that underlies its complex motions. But understanding turbulence and representing it artistically may be two different things. This video discusses some neat research that found that some of Vincent van Gogh’s paintings, like “The Starry Night”, display mathematical patterns like those of turbulence. (Video credit: TED Ed)
Piazza del Popolo
The lions of the fountain in Rome’s Piazza del Popolo eject a turbulent sheet of water. Random fluctuations in the water sheet cause holes to form. Driven by surface tension, these holes grow and merge, leaving behind ligaments of water which quickly break up into a spray of unevenly-sized drops. (Image credit: E. Villermaux)
Coalescence in Microgravity
Microgravity is a wonderful playground for fluid dynamics. Here astronaut Reid Wiseman demonstrates the interplay of forces involved in coalescence. When smaller droplets hit with insufficient force, they bounce off the water sphere. But if they hit hard enough to overcome surface tension, they coalesce with the sphere. I think the space station needs a high-speed video camera; I’d like to see this behavior at a few thousand frames per second! (Video credit: R. Wiseman/NASA)
APS DFD 2014
It’s that time of year again! Sunday marks the start of the 67th Annual Meeting of the American Physical Society Division of Fluid Dynamics. I’ll be in San Francisco for the full conference. On Sunday at 15:30 ET/12:30 PT I’ll be co-teaching a workshop on science communication alongside Flora Lichtman, David Hu, Rachel Levy, and Jason Bardi. We’ll be live-tweeting the event with the hashtag #DFDSciComm, and you are welcome to join in with comments and questions, even if you’re not attending the workshop in person. We’ll do our best to answer.
For those coming to the conference, keep an eye out and come say hello. I’ve got special FYFD stickers for those who do.
I expect to do some photos and short updates from the conference here, but for up-to-the-minute info on what I’m up to, your best bet is to follow the FYFD Twitter account. See you in California! (Image credits: N. Sharp/FYFD)
Pineapple Cavity
Objects falling into a quiescent fluid leave an air-filled cavity in their wake. The cavity collapses quickly due to the pressure of the surrounding fluid; but while it lasts, the cavity carries a signature of the object that made it. The collage above shows a series of snapshots of the formation and collapse of a cavity created by a 20-petal disk. Although the disk is essentially circular with only a small variation along its circumference, the effects of those perturbations appear soon after formation in the sidewalls of the cavity and persist until after its pinch-off and collapse. For more cavity dynamics, see here. (Image credit: O. Enriquez et al.)
Colonial Life
Hydroids are small underwater animals that often live in colonies made up of individual polyps. The colony is interconnected through the gastrovascular system, which is responsible for both digestion and respiration. In the images above, a single polyp in the colony has been fed food dyed with a fluorescent tracer. The polyp serves as a circulating pump and, as the food is digested and the tracer released, more and more of the colony becomes visible. Watch the full video and read more about the experiment. (Video credit and submission: L. Buss Lab)
The Rayleigh-Taylor Instability
What’s this? An FYFD video?! Yes, at long last, I’ve begun filming some videos of my own. This first one takes a look at the Rayleigh-Taylor instability and all that action that goes on in your coffee cup. I hope to bring you more FYFD-produced videos in the future, including some videos from the American Physical Society Division of Fluid Dynamics conference in San Francisco next week. What kind of topics would you guys be interested in for the future? (Video credit: N. Sharp)
“Cymatics”
Nigel Stanford’s new “Cymatics” music video is full of stunning science-inspired visuals. The entire video is set up around various science demos–many of which will be familiar to readers–that translate sound or vibration into visual elements. The video uses ferrofluids, vibrates vodka on a speaker to create Faraday waves, and visualizes resonant sound waves with a Rubens’ tube. I don’t want to give away all the awesome effects, so watch it for yourself, and then check out their behind-the-scenes page where they talk about how they created each effect. (Video credit: N. Stanford; submitted by buckitdrop)
Also, today is the final day of voting for the Vizzies, an NSF-sponsored contest for the best science and engineering visuals. Head over to their website to check out the finalists and choose your favorites!
Jet Impact
Viscoelasticity can generate some bizarre fluid behaviors. Viscoelastic fluids are special class of non-Newtonian fluid in which the response to deformation is both viscous, like a fluid, and elastic, like rubber. Above, a jet of viscoelastic fluid impacts a plate as viewed from the side (top image) and beneath (bottom image). When the jet impacts the plate, elastic stresses in the fluid destabilize the cylindrical symmetry of the jet. The jet instead becomes webbed, with an odd, asymmetric number of webs. The number of webs depends on the viscoelastic properties of the fluid as well as the jet’s speed and distance from the plate. (Image credit: B. Néel et al.)
