Defrosting and deicing surfaces is an energy-intensive affair, with lots of heat lost to warming up system components rather than the ice itself. In a new study, researchers explore a faster and more efficient method that focuses on heating just the interface. They coated their working surface in a thin layer of iridium tin oxide, a conductive film used in defrosting. Then, once the surface was iced over, they applied a 100 ms pulse of heating to the film. That localized heat melted the interface, and gravity pulled away the detached ice. Compared to conventional defrosting methods, this technique requires only 1% of the energy and 0.01% of the time. If the method scales reliably to applications like airplane deicing, it would provide enormous savings in time and energy. (Image and research credit: S. Chavan et al.)
Year: 2019
Boiling in Microgravity
In the playground of microgravity, every day processes can behave much differently. This photo comes from the RUBI experiment, the Reference mUltiscale Boiling Investigation, aboard the International Space Station. Freshly installed and switched on, the apparatus is now generating bubbles like this one. On the left, you see temperature sensors used to measure bubble temperatures. High-speed and infrared cameras are also part of the experiment.
The advantage of studying boiling in space is a lack of gravity that can mask or overwhelm subtler effects. It effectively slows down the process, making it easier to observe. And since boiling is such an important part of heat transfer in many manmade devices, it shows us how we have to adapt when operating in an environment where heat – and bubbles – don’t automatically rise. (Image credit: ESA; submitted by Kam-Yung Soh)
Champagne’s Shock Wave
The distinctive pop of opening a champagne bottle is more than the cork coming free. The sudden release of high-pressure gas creates a freezing jet that’s initially supersonic. It even creates a Mach disk, like those seen in rocket exhaust. That supersonic flow can only be maintained, though, with a large enough pressure difference between the gas in the bottle and the atmosphere outside. Once the pressure drops below that critical point, the jet slows down and becomes subsonic. For more on champagne popping and its colorful plume, check out this previous post. (Image and research credit: G. Liger-Belair et al.; via Nature; submitted by Kam-Yung Soh)
Waves on a Supercell
This Colorado supercell thunderstorm features an unusual twist. Notice the sawtooth-like protrusions along the outer cloud wall. These are Kelvin-Helmholtz waves, like these fair-weather clouds we’ve seen before, but instead of occurring vertically, they project horizontally! That implies that the invisible layer of air just outside the cloud wall is moving faster than the wall itself. That creates shear along the outer edge of the cloud wall and causes these waves to form. This is the first time I’ve ever seen this sort of thing. What an awesome photo! (Image credit: M. Charnick; submitted by jpshoer)
Crowds as a Fluid
At a low density, crowds of people can behave like a fluid, which has led to numerous hydrodynamically-based crowd models. At higher densities, though, crowds are more like a soft solid, and researchers are adapting models developed for granular materials like sand to describe these crowds. In granular materials, these models help scientists identify how vibrations move through the complex network of grains and what circumstances might cause sudden reorganizations. In a large crowd, this could tell scientists the difference between the innocuous shuffle at a rock concert and the trigger for a deadly stampede. Getting real-world data for comparison is tough – obviously, it’s unethical to intentionally cause a crowd to panic – so thus far the models remain relatively untested. (Image credit: M. Lebrun; research credit: A. Bottinelli and J. Silverberg)
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
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)
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
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
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)
