FYFD

Tag: fluid dynamics

  • Featured Video Play Icon

    Getting Cold

    Just as some chemical reactions produce heat, many chemical combinations absorb heat. In “Getting Cold,” the Beauty of Science team demonstrates this by showing endothermic processes in both visible and infrared light. Combinations that appear humdrum from our normal perspective suddenly become vibrant and interesting when we see the temperature variations accompanying them. 

    Evaporation is a good example. As humans, we sweat so that when our sweat evaporates off our skin, it takes heat away with it. Water (the main ingredient in sweat) isn’t the fastest evaporating liquid, however. Here it’s shown alongside ethyl acetate, a common ingredient in nail polish remover. And anyone who’s used nail polish remover is familiar with the chill it leaves behind as it evaporates. Just look how much colder and darker it is when evaporating! (Video and image credit: Beauty of Science)

  • Explosive Flame Fronts

    Explosive Flame Fronts

    Though they look like jellyfish or space creatures, these images from photographer Linden Gledhill are actually explosions. What you’re seeing is the detonation of hydrogen gas with oxygen. The teal sphere with its wavy surface marks the flame front, and the crisp, stringy edges seen here and there in the foreground are the remains of a soap bubble that held the hydrogen before it sparked. You can see a similar set-up (using methane rather than hydrogen) in action here, and you can see other artistic takes on combustion in previous posts like this one. (Image credit: L. Gledhill, Flickr)

  • Featured Video Play Icon

    Calimero’s Uprising!

    Here on FYFD posts often focus on research results, with animations and images showing only a tiny portion of the apparatus necessary to conduct that work. But in this timelapse, we get to see a glimpse of what it takes to make the research happen. The video covers a 12-week period in which student Sietze Oostveen sets up, modifies, and takes measurements with a rotating tank apparatus called Calimero. 

    The video captions give you a sense of all the little tasks that go into experimental work, from installing thermal control and measurement systems (in this case, laser Doppler velocimetry, or LDV) to making sure that the rotating table is balanced correctly. In experimental work, it’s worth remembering that you’ll likely spend as much or more time preparing to take data than you will actually doing measurements! (Video credit: S. Oostveen/UCLA Spinlab)

  • The Drama of Turbulence

    The Drama of Turbulence

    Photographer Jason Wright captures dramatic views of Hawaiian landscapes. Moments like these remind us of the spectacular power of the ocean and atmosphere around us. Just look at all that incredible turbulence! See more of Wright’s work on his Instagram and website. (Image credit: J. Wright; via Colossal)

  • Superheating

    Superheating

    Being hot isn’t always enough to make water boil. To form vapor bubbles, water and other liquids need imperfections that serve as seeds. In the absence of these, the liquid can become superheated, reaching temperatures higher than its boiling point without forming bubbles. Superheated water can be quite dangerous because it appears to be cooler, but once it’s disturbed – thereby breaking its surface tension – vapor bubbles form rapidly and explosively. You can see in the animation above just how quickly and unsteadily a sudden vapor bubble expands as it rises to the surface. (Image credit: C. Kalelkar and K. Raj, source)

  • Waterspouts

    Waterspouts

    Despite their ominous appearance, these waterspouts – like most of their kind – are fair-weather phenomena unrelated to tornadoes. They can form when cold, dry air moves over warm waters. As warm, moist air rises from the water’s surface, air is drawn in from the surroundings to replace it. Any vorticity in that air comes with it, growing stronger as it gets pulls in, thanks to conservation of angular momentum. That action creates the waterspout, which becomes visible when the warm, humid air cools enough to condense and form a cloud wall. (Image credit: R. Giudici; via EPOD)

  • Avoiding Shear Thickening

    Avoiding Shear Thickening

    Many substances – like the cornstarch and water mixture above – exhibit a property called shear-thickening. In these fluids, deforming them quickly causes the viscosity to increase dramatically. That shear-thickening occurs when particles inside the fluid jam together, creating large chains able to resist the force being applied. That’s why the oobleck on this vibrating speaker can sustain these “cornstarch monsters”.

    Shear-thickening is useful in many contexts, but it’s problematic during manufacturing, when pumping these substances can become incredibly difficult due to the fluid’s innate resistance to flowing. A new study, though, finds that it’s possible to temporarily suppress shear-thickening using acoustic waves. The researchers used piezoelectric devices to generate acoustic waves at a frequency around 1 MHz while shearing the cornstarch mixture. The acoustic waves disrupt the formation of particle chains inside the mixture, keeping its viscosity 10 times lower than during regular shear-thickening. (Image credit: bendhoward, source; research credit: P. Sehgal et al.; submitted by Brian K.)

  • Seeing Sound

    Seeing Sound

    It’s not always easy to imagine how waves travel, but with this demonstration, you can see sound waves and how they reflect and defract. The set-up uses schlieren optics that show light and dark bands where strong changes in density take place. This, combined with a stroboscopic light, makes it possible to see the wave fronts from the acoustic transducer on the left side of the screen. Once the wave is apparent, introducing a reflective object lets us see exactly how sound waves bounce, reflect, and interfere. (Image and video credit: Harvard Natural Sciences Lecture Demonstrations)

  • Making Giant Soap Bubbles

    Making Giant Soap Bubbles

    Making soap bubbles is fun, but there’s something about gigantic soap bubbles that brings out the child in everyone. The world’s largest freestanding soap bubble had more than 100 square meters of surface area, which begs an important question: how can such a thin film stay stable at that size?

    The solutions used for giant bubbles have a few main ingredients: water, naturally; detergent, used for its surfactants; and polymers like polyethylene glycol that help stabilize the soap film. Exactly why polymers helped was a bit of mystery, but a new pre-print study aims to answer that.

    Researchers studied how polymer concentrations affected 1) how much solution could be drawn in as bubbles formed, and 2) how long a film of solution lasted before gravity and evaporation thinned it to breaking. They found that intermediate polymer concentrations actually worked best. This gave the solution the viscoelasticity needed to draw in more solution as bubbles grew without having so much polymer that it negatively affected film lifetime. (Image credit: Pixabay; research credit: S. Frazier et al.; via MIT Tech Review; submitted by Kam-Yung Soh)

  • Featured Video Play Icon

    How to Build a Lava Moat

    If you’re looking for a new and impractical way to protect your home, here’s a great option: a lava moat. Nothing says “Don’t try to knock on my door” like a glowing inferno of molten rock. And Minute Physics – along with xkcd – has put together a short, handy guide to some of the challenges you’ll face in building and maintaining this fearsome fortification. If running your own commercial-scale power plant seems overly daunting but you still want to see what lava’s all about, I have good news; here’s a selection of some of my favorite looks at lava here at FYFD:

    – Upstate NY’s homemade lava
    – What happens when you step on lava
    –  A veritable river of lava in action
    – What happens when water meets lava

    Now, if you’ll excuse me, I’m off to Hawai’i for the next two weeks. There will be lava. (Video credit: Minute Physics)