FYFD

Month: November 2014

  • Wave Clouds

    Wave Clouds

    Coming home from APS DFD, I looked out the window as we flew east over the last of the Rockies and caught these wave clouds. Air flowing west to east gets disturbed by the mountains, which creates internal waves in the atmosphere. Generally, these are invisible–though they can cause some of the turbulence you feel when flying. In this case, water vapor has condensed at the crests of the internal waves, creating a pattern of cloudy and clear stripes to mark the waves. The internal waves damped out by the time we flew a couple hundred miles east of Denver, but for awhile conditions were just right. (Photo credit: N. Sharp)

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    Supercooling Water

    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)

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    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

    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

    Click through to see.

    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)

  • DFD Reminder

    Reminder: APS DFD is starting today. Follow along on Twitter at @fyfluiddynamics and . Later today at 12:30 PT you can follow our science communication workshop and ask questions at #DFDSciComm.

  • APS DFD 2014

    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

    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

    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)

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    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)