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  2. <rss xmlns:dc="" version="2.0"><channel><description>Celebrating the physics of all that flows. Ask a question, submit a post idea or send an email. You can also follow FYFD on Twitter and YouTube. FYFD is written by Nicole Sharp, PhD.If you’re a fan of FYFD and would like to help support the site and its outreach, please consider becoming a patron on Patreon or giving a donation through PayPal with the button below. Your support is much appreciated!
  3. </description><title>FYFD</title><generator>Tumblr (3.0; @fuckyeahfluiddynamics)</generator><link></link><item><title>Resonance is a funny creature, as Dianna discovered when she...</title><description>&lt;iframe width="400" height="225"  id="youtube_iframe" src=";enablejsapi=1&amp;origin=;wmode=opaque" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen&gt;&lt;/iframe&gt;&lt;br/&gt;&lt;br/&gt;&lt;p&gt;&lt;a href=""&gt;Resonance&lt;/a&gt; is a funny creature, as Dianna discovered when she tried to sing a rising scale through a tube. At certain notes, everyone who attempted to do it had their voices crack. Tracking down the source of the mystery means digging into what exactly resonance is and what the differences are between driving a system just before, at, and after resonance. Check out the video for the full acoustic story. (Video credit: Physics Girl)&lt;/p&gt;</description><link></link><guid></guid><pubDate>Mon, 20 May 2019 10:00:10 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>acoustics</category><category>music</category><category>sciblr</category><category>resonance</category><category>Helmholtz resonance</category></item><item><title>The bunchberry dogwood, unlike its taller relatives, is a...</title><description>&lt;img src=""/&gt;&lt;br/&gt;&lt;br/&gt;&lt;p&gt;The &lt;a href=""&gt;bunchberry dogwood&lt;/a&gt;, unlike its taller relatives, is a low-lying subshrub that spreads along the ground. But it sports some of the fastest action of any &lt;a href=""&gt;plant&lt;/a&gt;, requiring 10,000 frames per second to capture! When young buds form in the bunchberry flower, their four petals are fused, completely hiding the stamens. As the plant matures, the pollen-carrying stamens grow faster than the petals, causing them to peek out the sides of the bud. But the petals stay attached at the tip, holding the stamens in while &lt;a href=""&gt;pressure&lt;/a&gt; inside the stamens creates a store of elastic energy. &lt;/p&gt;&lt;p&gt;When disturbed, the petals break loose and the stamens spring up and out. The anthers at their tips hold the pollen in place until the stamen reaches its maximum vertical velocity, at which point the anthers swing out to release the pollen upward. In essence, the flower works in the same manner as a trebuchet, flinging pollen with an acceleration 2,400 times greater than gravity. That’s enough to coat pollen onto nearby insects and to launch the remainder high enough for the wind to catch it. (Image and research credit: &lt;a href=""&gt;D. Whitaker et al.&lt;/a&gt;, &lt;a href=""&gt;source&lt;/a&gt;; via &lt;a href=""&gt;Science News&lt;/a&gt;; submitted by &lt;a href=""&gt;Kam-Yung Soh&lt;/a&gt;)&lt;/p&gt;&lt;p&gt;&lt;small&gt;And with that, FYFD’s Plant Week is a wrap! Missed one of the previous posts? You can catch up with them &lt;a href=""&gt;here&lt;/a&gt;.&lt;/small&gt;&lt;/p&gt;</description><link></link><guid></guid><pubDate>Fri, 17 May 2019 10:00:27 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>plants</category><category>biology</category><category>botany</category><category>elasticity</category><category>turgor pressure</category><category>wind</category></item><item><title>Bartenders and citrus lovers the world over are familiar with...</title><description>&lt;img src=""/&gt;&lt;br/&gt;&lt;br/&gt;&lt;p&gt;Bartenders and citrus lovers the world over are familiar with the mist of oil that bursts from a bent citrus peel. These microjets are about the width of a human hair, but they can spray at nearly 30 m/s in some citrus species. That’s an acceleration g-force of more 5,100, comparable to a bullet fired from a gun! &lt;/p&gt;&lt;p&gt;The key to the jets is the structure of the fruit’s peel. Citrus fruits have a relatively thick, soft inner material, known as the albedo, which houses the oil reservoirs. The thin, stiff outer layer of the peel, called the flavedo or zest, covers that. When the peel is bent, the albedo compresses, increasing the pressure inside the oil reservoirs up to an additional atmosphere’s worth. Meanwhile, the flavedo is stretched. When that outer layer fails, it releases the oil pressure and a jet spurts out. For more on this work, including some awesome high-speed videos, check out my interview (&lt;a href=""&gt;starting at 2:59&lt;/a&gt;) with one of the authors in the video below. (Image and research credit: &lt;a href=""&gt;N. Smith et al.&lt;/a&gt;; video credit: N. Sharp and T. Crawford)&lt;/p&gt;&lt;p&gt;&lt;small&gt;FYFD is celebrating Plant Week all this week. Check out our previous posts on &lt;a href=""&gt;how moisture lets horsetail plant spores walk and jump&lt;/a&gt;, &lt;a href=""&gt;the incredible aerodynamics of dandelion seeds&lt;/a&gt;, and the &lt;a href=""&gt;ultra-fast suction bladderworts use to hunt&lt;/a&gt;.&lt;/small&gt;&lt;/p&gt;&lt;figure class="tmblr-embed tmblr-full" data-provider="youtube" data-orig-width="540" data-orig-height="304" data-url=""&gt;&lt;iframe width="540" height="304" id="youtube_iframe" src=";enablejsapi=1&amp;origin=;wmode=opaque" frameborder="0" allowfullscreen="allowfullscreen"&gt;&lt;/iframe&gt;&lt;/figure&gt;</description><link></link><guid></guid><pubDate>Thu, 16 May 2019 10:00:25 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>citrus</category><category>microfluidics</category><category>jets</category><category>plants</category></item><item><title>You might think that plants are pretty stationary, but they have...</title><description>&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;p&gt;You might think that &lt;a href=""&gt;plants&lt;/a&gt; are pretty stationary, but they have evolved a myriad of ways of moving, especially when it comes to spreading their seeds and spores. Shown above is the spore of the horsetail plant, a spherical pod with four, ribbon-like elators that are moisture-sensitive. When exposed to water, the elators curl around the spore, but as they dry out, they unfurl (top). Repeated cycles of this allows the spores to “walk” short distances (middle). And, if the elators deploy quickly, the spore can even “jump” (bottom). Researchers recorded jumps high enough for the spores to catch a breeze and disperse further. For similar moisture-driven plant action, &lt;a href=""&gt;check out this seed that buries itself&lt;/a&gt;! (Image and research credit: &lt;a href=""&gt;P. Marmonttant et al.&lt;/a&gt;, &lt;a href=""&gt;source&lt;/a&gt;; via &lt;a href=""&gt;Science News&lt;/a&gt;; submitted by &lt;a href=""&gt;Kam-Yung Soh&lt;/a&gt;)&lt;/p&gt;&lt;p&gt;&lt;small&gt;We’re celebrating botanically-based physics all this week with Plant Week. Check out our previous posts on the &lt;a href=""&gt;ultra-fast suction of carnivorous bladderworts&lt;/a&gt; and the &lt;a href=""&gt;incredible flight of dandelion seeds&lt;/a&gt;.&lt;/small&gt;&lt;/p&gt;</description><link></link><guid></guid><pubDate>Wed, 15 May 2019 10:00:13 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>biology</category><category>botany</category><category>plants</category><category>sciblr</category><category>spores</category></item><item><title>Carnivorous plants live in nutrient-poor environments, where...</title><description>&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;p&gt;Carnivorous &lt;a href=""&gt;plants&lt;/a&gt; live in nutrient-poor environments, where clever techniques are necessary to keep their prey from getting away. The aquatic bladderwort family nabs their prey through ultra-fast &lt;a href=""&gt;suction&lt;/a&gt;. This starts with a slow phase (top) in which water is pumped out of the trap. Because the internal pressure is lower than the external hydrostatic pressure, this compresses the walls of the trap, and it leaves the trap’s door narrowly balanced on the edge of stability. A slight perturbation to the trigger hairs around the door will cause it to buckle. &lt;/p&gt;&lt;p&gt;That’s when things get fast. As the door buckles and the trap expands to its original volume, water gets sucked in, pulling whatever prey was nearby with it. The door reseals as the pressure inside and outside the trap equalizes, and, in only a couple milliseconds total, the bladderwort has its snack. It secretes digestive enzymes to break down what it’s caught, and over many hours, it pumps out the trap to reset it. (Image and research credit: &lt;a href=""&gt;O. Vincent et al.&lt;/a&gt;; submitted by &lt;a href=""&gt;David B.&lt;/a&gt;)&lt;/p&gt;&lt;p&gt;&lt;small&gt;All this week, FYFD is celebrating Plant Week. Check out our previous post on &lt;a href=""&gt;how dandelion seeds fly tens of kilometers&lt;/a&gt;.&lt;/small&gt;&lt;/p&gt;</description><link></link><guid></guid><pubDate>Tue, 14 May 2019 10:00:14 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>biology</category><category>botany</category><category>bladderwort</category><category>plants</category><category>suction</category><category>buckling</category><category>pressure</category></item><item><title>To kick off Plant Week here on FYFD, we’re taking a closer look...</title><description>&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;p&gt;To kick off Plant Week here on FYFD, we’re taking a closer look at that ubiquitous flower: the dandelion. Love ‘em or hate ‘em, these little guys manage to get just about everywhere, thanks in part to their amazing ability to stay windborne for up to 150 km! To do that, the dandelion uses a bristly umbrella of tiny filaments, known as a pappus, that can generate more than four times the drag per area of a solid disk. Its porosity – all that empty space between the filaments – is also key to its stability; it helps create and stabilize a separated vortex ring that the seed uses to stay aloft. Check out the full video below! (Image and video credit: N. Sharp)&lt;/p&gt;&lt;figure class="tmblr-embed tmblr-full" data-provider="youtube" data-orig-width="540" data-orig-height="304" data-url=""&gt;&lt;iframe width="540" height="304" id="youtube_iframe" src=";enablejsapi=1&amp;origin=;wmode=opaque" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen=""&gt;&lt;/iframe&gt;&lt;/figure&gt;</description><link></link><guid></guid><pubDate>Mon, 13 May 2019 10:00:19 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>biology</category><category>sciblr</category><category>botany</category><category>plants</category><category>plant week</category><category>dandelion</category><category>aerodynamics</category><category>vortex ring</category><category>separated vortex ring</category><category>porosity</category><category>drag generation</category></item><item><title>Spring has sprung! The trees have leaves, the flowers are in...</title><description>&lt;img src=""/&gt;&lt;br/&gt;&lt;br/&gt;&lt;p&gt;Spring has sprung! The trees have leaves, the flowers are in bloom, and snow is (almost) a distant memory.* And here at FYFD, we’re getting ready to kick off a full week of celebrating the intersection of fluid dynamics and plants. &lt;/p&gt;&lt;p&gt;To get you into the mood, here’s a look at some previous plant-filled posts:&lt;/p&gt;&lt;p&gt;- &lt;a href=""&gt;How trees use negative pressure to hydrate&lt;/a&gt;&lt;br/&gt;- &lt;a href=""&gt;The catapulting seeds of the hairyflower wild petunia&lt;/a&gt;&lt;br/&gt;- &lt;a href=""&gt;Seeds that self-dig&lt;/a&gt;&lt;br/&gt;- &lt;a href=""&gt;How desert moss drinks from the air&lt;/a&gt;&lt;br/&gt;- &lt;a href=""&gt;The swimming of zoospores&lt;/a&gt;&lt;br/&gt;&lt;/p&gt;&lt;p&gt;Stay tuned all next week for lots more plant physics!&lt;/p&gt;&lt;p&gt;*Confession: it’s still snowing at my house as I type this. But the trees &lt;i&gt;do&lt;/i&gt; have leaves and there &lt;i&gt;are&lt;/i&gt; flowers blooming. Poor things. - Nicole&lt;/p&gt;&lt;p&gt;
  5. (Original image: &lt;a href=""&gt;Pixabay&lt;/a&gt;)
  7. &lt;br/&gt;&lt;/p&gt;</description><link></link><guid></guid><pubDate>Fri, 10 May 2019 10:00:09 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>biology</category><category>botany</category><category>plant week</category></item><item><title>Among objects in our solar system, the Moon is rather unusual....</title><description>&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;p&gt;Among objects in our solar system, the Moon is rather unusual. It’s the only large moon paired with a rocky planet, and only &lt;a href=""&gt;Pluto&lt;/a&gt;’s Charon boasts a larger size relative to its planet. Chemically speaking, the Moon is also extremely similar to the Earth, which is part of why scientists theorized that the moon coalesced after the proto-Earth collided with a Mars-sized object. But lingering questions remained, like why the Moon is rich in iron oxide compared to the Earth.&lt;/p&gt;&lt;p&gt;&lt;a href=""&gt;A new study&lt;/a&gt; tweaks the idea of the giant impactor by adding a magma ocean to the proto-Earth. In the early days of the solar system, collisions were so common that larger bodies (&gt; 2*Mars) probably maintained a molten ocean. By simulating collisions with and without a magma ocean and studying the final composition of these simulated Earth-Moon-systems, the researchers found that a molten ocean not only matches the expected size and orbital characteristics of the two bodies, but the results reflect the actual chemical make-up of the  real Earth and Moon, too! (Image credits: moon - &lt;a href=""&gt;N. Thomas&lt;/a&gt;, impact simulation - &lt;a href=""&gt;N. Hosono et al.&lt;/a&gt;; research credit: &lt;a href=""&gt;N. Hosono et al.&lt;/a&gt;; via &lt;a href=""&gt;Ars Technica&lt;/a&gt;; submitted by &lt;a href=""&gt;Kam-Yung Soh&lt;/a&gt;)&lt;/p&gt;</description><link></link><guid></guid><pubDate>Thu, 09 May 2019 10:00:27 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>geology</category><category>planetary science</category><category>numerical simulation</category><category>asteroid impact</category><category>Moon</category></item><item><title>Granular mixtures show surprising similarities to fluids, even...</title><description>&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;p&gt;&lt;a href=""&gt;Granular mixtures&lt;/a&gt; show surprising similarities to fluids, even though their underlying physics differ. The latest example of this is a &lt;a href=""&gt;Rayleigh-Taylor-like instability&lt;/a&gt; that occurs when heavy particles sit atop lighter ones. By combining vertical &lt;a href=""&gt;vibration&lt;/a&gt; and an &lt;a href=""&gt;upward gas flow&lt;/a&gt;, researchers found that the lighter particles form fingers and bubbles that seep up between the heavier grains (upper left). Visually, it looks remarkably similar to a lava lamp or other Rayleigh-Taylor-driven instability (upper right).&lt;/p&gt;&lt;p&gt;But the physics behind the two are distinctly different. In the fluid, buoyancy drives the instability while surface tension acts as a stabilizing force. There’s no surface tension in a granular material, though. Instead, the drag force from gas flowing upward provides the vertical impetus while friction between the grains – essentially an effective viscosity – replaces surface tension as a stabilizing influence.&lt;/p&gt;&lt;p&gt;The similarities don’t stop there, though. When the researchers tested a “bubble” of heavy grains suspended in lighter ones (lower left), they found that, instead of sinking, the granular bubble split in two and drifted downward on a diagonal. Eventually, those daughter bubbles also split. Again, visually, this looks a lot like what happens to a drop of ink or food coloring falling through water (lower right), but the physics aren’t the same at all. &lt;/p&gt;&lt;p&gt;In the fluid, the breakup happens when a falling vortex ring splits. In the granular example, gas moving upward tends to channel around the heavy grains because they’re harder to move through. Eventually, this builds up a solidified region under the bubble. When the heavy grains can’t move directly down, they split and sink through the surrounding suspended particles until they build up another jammed area and have to split again. (Image credits: granular RTI - &lt;a href=""&gt;C. McLaren et al.&lt;/a&gt;; RTI simulation - &lt;a href=""&gt;M. Stock&lt;/a&gt;; bag instability - &lt;a href=""&gt;D. Zillis&lt;/a&gt;; research credit: &lt;a href=""&gt;C. McLaren et al.&lt;/a&gt;; submitted by &lt;a href=""&gt;Kam-Yung Soh&lt;/a&gt;)&lt;/p&gt;</description><link></link><guid></guid><pubDate>Wed, 08 May 2019 10:00:26 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>granular material</category><category>granular flow</category><category>instability</category><category>Rayleigh-Taylor instability</category><category>fluidization</category><category>buoyancy</category><category>vibration</category><category>flow visualization</category></item><item><title>For a droplet to bounce, we expect it to hit a wall or a sharp...</title><description>&lt;img src=""/&gt;&lt;br/&gt;&lt;br/&gt;&lt;p&gt;For a droplet to bounce, we expect it to &lt;a href=""&gt;hit a wall&lt;/a&gt; or a &lt;a href=""&gt;sharp interface&lt;/a&gt; of some kind. But in a &lt;a href=""&gt;new study&lt;/a&gt;, researchers demonstrate a droplet that bounces with neither. Shown above is an oil droplet sinking through a stratified mixture of ethanol (toward the top) and water (toward the bottom). Because the oil is heavier than ethanol, it initially sinks, dragging some of the ethanol with it as it falls. Over time, some of that ethanol rises again, forming what’s known as a buoyant jet.&lt;/p&gt;&lt;p&gt;Simultaneously, the gradient of ethanol to water between the top and bottom of the drop creates an imbalance in surface tension. The ethanol near the top of the drop has a lower surface tension than the water at the bottom. This creates a downward &lt;a href=""&gt;Marangoni flow&lt;/a&gt; along the drop interface. &lt;/p&gt;&lt;p&gt;The bounce itself happens quickly after a long, slow sinking period. As the drop’s sinking slows, the buoyant jet weakens until it disappears completely. At the same time, the downward Marangoni flow pulls fresh ethanol-rich fluid toward the top of the drop. That increases the surface tension difference and strengthens the Marangoni flow, creating a positive feedback loop. In less than a second, the Marangoni flow increases by two orders of magnitude, pulling so hard that the drop shoots upward. &lt;/p&gt;&lt;p&gt;That resets the cycle by weakening the Marangoni flow and strengthening the buoyant jet. The droplet can continue bouncing for about 30 minutes until the concentration gradient is so well-mixed that the cycle can’t continue. (Image and research credit: &lt;a href=""&gt;Y. Li et al.&lt;/a&gt;; via &lt;a href=""&gt;APS Physics&lt;/a&gt;; submitted by &lt;a href=""&gt;Kam-Yung Soh&lt;/a&gt;)&lt;/p&gt;</description><link></link><guid></guid><pubDate>Tue, 07 May 2019 10:00:17 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>droplets</category><category>stratification</category><category>marangoni effect</category><category>surface tension</category><category>buoyancy</category></item><item><title>Beautiful as a splash is, why only enjoy it from a single angle?...</title><description>&lt;iframe width="400" height="225"  id="youtube_iframe" src=";enablejsapi=1&amp;origin=;wmode=opaque" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen&gt;&lt;/iframe&gt;&lt;br/&gt;&lt;br/&gt;&lt;p&gt;Beautiful as a &lt;a href=""&gt;splash&lt;/a&gt; is, why only enjoy it from a single angle? In this video, the artists behind Macro Room offer a 360-degree perspective on various splashes and fluid collisions. I especially enjoy watching the splash &lt;a href=""&gt;crowns&lt;/a&gt; falling back over and out of the various containers they use. What’s your favorite part? (Image and video credit: Macro Room)&lt;/p&gt;&lt;figure data-orig-width="540" data-orig-height="304" class="tmblr-full"&gt;&lt;img src="" alt="image" data-orig-width="540" data-orig-height="304"/&gt;&lt;/figure&gt;&lt;figure data-orig-width="540" data-orig-height="304" class="tmblr-full"&gt;&lt;img src="" alt="image" data-orig-width="540" data-orig-height="304"/&gt;&lt;/figure&gt;&lt;figure data-orig-width="540" data-orig-height="304" class="tmblr-full"&gt;&lt;img src="" alt="image" data-orig-width="540" data-orig-height="304"/&gt;&lt;/figure&gt;</description><link></link><guid></guid><pubDate>Mon, 06 May 2019 10:00:22 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>fluids as art</category><category>splash</category><category>splashes</category><category>splashing</category><category>granular material</category></item><item><title>One of the challenges in studying tornadoes is being in the...</title><description>&lt;img src=""/&gt;&lt;br/&gt;&lt;br/&gt;&lt;p&gt;One of the challenges in studying &lt;a href=""&gt;tornadoes&lt;/a&gt; is being in the right place at the right time. In that regard, storm chaser Brandon Clement hit the jackpot earlier this week when he captured this footage of a tornado near Sulphur, Oklahoma from his drone. He was able to follow the twister for several minutes until it apparently dissipated. &lt;/p&gt;&lt;p&gt;Scientists are still uncertain exactly how tornadoes form, but they’ve learned to recognize the key ingredients. A strong variation of wind speed with altitude can create a horizontally-oriented vortex, which a localized &lt;a href=""&gt;updraft&lt;/a&gt; of warm, moist air can lift and rotate to vertical, birthing a tornado. These storms most commonly occur in the central U.S. and Canada during springtime, and researchers are actively pursing new ways to predict and track tornadoes, including &lt;a href=""&gt;microphone arrays capable of locating them before they fully form&lt;/a&gt;. (Image and video credit: &lt;a href=""&gt;B. Clement&lt;/a&gt;; via &lt;a href=""&gt;Earther&lt;/a&gt;)&lt;/p&gt;&lt;figure class="tmblr-embed tmblr-full" data-provider="youtube" data-orig-width="540" data-orig-height="304" data-url=""&gt;&lt;iframe width="540" height="304" id="youtube_iframe" src=";enablejsapi=1&amp;origin=;wmode=opaque" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen=""&gt;&lt;/iframe&gt;&lt;/figure&gt;</description><link></link><guid></guid><pubDate>Fri, 03 May 2019 10:00:05 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>meteorology</category><category>tornado</category><category>vortex</category><category>weather</category><category>flow visualization</category></item><item><title>Pattern formation is extremely common in nature, from the...</title><description>&lt;img src=""/&gt;&lt;br/&gt;&lt;br/&gt;&lt;p&gt;Pattern formation is extremely common in nature, from the dendritic growth of trees and snowflakes to the stripes of a tiger. &lt;a href=""&gt;A new paper describes&lt;/a&gt; how a thin layer of ice in a liquid can form labyrinthine patterns when illuminated with near-infrared light. Both the liquid and ice are maintained at a constant temperature below the melting point, but the ice absorbs the near-infrared light more effectively than the water. This means that parts of the ice that are far from the liquid warm and melt faster, creating holes that can then allow a pocket of liquid to seep in and reduce the absorption rate. The ice crystals themselves thin and expand across the surface at the expense of more holes, which eventually create larger channels that pock the ice. (Image and research credit: &lt;a href=""&gt;S. Preis et al.&lt;/a&gt;; via &lt;a href=""&gt;Nature&lt;/a&gt;; submitted by &lt;a href=""&gt;Kam-Yung Soh&lt;/a&gt;)&lt;/p&gt;</description><link></link><guid></guid><pubDate>Thu, 02 May 2019 10:00:08 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>freezing</category><category>ice</category><category>multiphase</category><category>melting</category><category>pattern formation</category></item><item><title>When it comes to the aerodynamics of cars, there’s only so much...</title><description>&lt;img src=""/&gt;&lt;br/&gt;&lt;br/&gt;&lt;p&gt;When it comes to the aerodynamics of cars, there’s only so much &lt;a href=""&gt;streamlining&lt;/a&gt; one can do. In the end, most cars have a certain boxy-ness as a matter of practicality; they do, after all, have to carry people and things. But that doesn’t mean we’re stuck with the level of drag those shapes entail.&lt;/p&gt;&lt;p&gt;For cars and other non-streamlined objects, much of their drag comes from their &lt;a href=""&gt;wake&lt;/a&gt;, which usually contains a large, asymmetric, and unsteady &lt;a href=""&gt;recirculation&lt;/a&gt; region. In a &lt;a href=""&gt;new wind tunnel study&lt;/a&gt;, scientists used air blasts to reshape this wake, making it more symmetrical, even when the wind direction did not align with the car model. That reduced the drag by 6%. They’re now experimenting with adding additional nozzles along the non-windward edges of the model to see if they can reduce drag even further. &lt;/p&gt;&lt;p&gt;Although this appears to be the first time this technique has been tested for road vehicles, the idea of &lt;a href=""&gt;blowing air to improve aerodynamics&lt;/a&gt; is well-established, particularly in aviation. (Image credit: &lt;a href=""&gt;V. Malagoli&lt;/a&gt;; research credit: &lt;a href=""&gt;R. Li et al.&lt;/a&gt;, submitted by Marc A.)&lt;/p&gt;</description><link></link><guid></guid><pubDate>Wed, 01 May 2019 10:00:29 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>cars</category><category>drag reduction</category><category>blowing</category><category>wake</category></item><item><title>On bodies around the solar system, there are craters marking...</title><description>&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;p&gt;On bodies around the solar system, there are craters marking billions of years’ worth of impacts. Many of these craters have rays–distinctive lines radiating out from the point of impact. But if you drop an object onto a smooth &lt;a href=""&gt;granular surface&lt;/a&gt; (upper left), the ejecta form a uniform splash with no rays. The impactor must hit a roughened surface (upper right) in order to leave rays. &lt;/p&gt;&lt;p&gt;Through experiment and simulation, researchers found that the rays emanate from valleys in the surface that come in contact with the impactor. Moreover, the number of rays that form depends only on the size of the impactor and the undulations of the surface. That means that, by knowing the topography of a planetary body and counting the number of rays left behind, scientists can now estimate what the size of the object that struck was! (Image, video, and research credit: &lt;a href=""&gt;T. Sabuwala et al.&lt;/a&gt;)&lt;/p&gt;&lt;figure class="tmblr-embed tmblr-full" data-provider="youtube" data-orig-width="540" data-orig-height="304" data-url=""&gt;&lt;iframe width="540" height="304" id="youtube_iframe" src=";enablejsapi=1&amp;origin=;wmode=opaque" frameborder="0" allowfullscreen=""&gt;&lt;/iframe&gt;&lt;/figure&gt;</description><link></link><guid></guid><pubDate>Tue, 30 Apr 2019 10:00:28 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>geology</category><category>geophysics</category><category>planetary science</category><category>scibl</category><category>splashes</category><category>granular material</category><category>ejecta</category><category>asteroid impact</category><category>sciblr</category></item><item><title>Known as ebru in Turkey and suminagashi in Japan, the art of...</title><description>&lt;iframe width="400" height="225"  id="youtube_iframe" src=";enablejsapi=1&amp;origin=;wmode=opaque" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen&gt;&lt;/iframe&gt;&lt;br/&gt;&lt;br/&gt;&lt;p&gt;Known as ebru in Turkey and suminagashi in Japan, the art of &lt;a href=""&gt;paper marbling&lt;/a&gt; has flourished in cultures around the world since medieval times. The details of methods vary, but in general, the technique uses a base of oily water to float various dyes and pigments. Artists then use brushes, wires, and other tools to manipulate the dyes into the desired pattern. Paper is spread over the top to soak up the color pattern before being hung to dry. Every print made in this manner is a unique result of buoyancy, surface tension variation, and viscous manipulation. Check out the video above to watch a timelapse video showing the technique in action. (Video and image credit: Royal Hali)&lt;/p&gt;&lt;figure data-orig-width="1280" data-orig-height="720" class="tmblr-full"&gt;&lt;img src="" alt="image" data-orig-width="1280" data-orig-height="720"/&gt;&lt;/figure&gt;</description><link></link><guid></guid><pubDate>Mon, 29 Apr 2019 10:00:21 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>suminagashi</category><category>ebru</category><category>paper marbling</category><category>fluids as art</category><category>buoyancy</category><category>viscous flow</category><category>Marangoni effect</category></item><item><title>When they evaporate, drops of liquids like coffee and red wine...</title><description>&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;img src=""/&gt;&lt;br/&gt; &lt;br/&gt;&lt;p&gt;When they evaporate, drops of liquids like coffee and red wine &lt;a href=""&gt;leave behind stains with a darker ring along the edges&lt;/a&gt;, thanks to capillary action and surface tension pulling particles to that outer edge. In contrast, sublimating a frozen droplet leaves a stain pattern that concentrates at the center (top).
  9. &lt;a href=""&gt;When droplets freeze from the surface upward&lt;/a&gt;, particles within the droplet are driven toward the center as the freeze front pushes toward the drop apex. The final shape of the stain depends on the initial geometry of the droplet, and the concentration of particles toward the center occurs because of the way that the particle freezes, not how it sublimates (bottom). &lt;/p&gt;&lt;p&gt;Since many industrial processes rely on droplet evaporation to spread coatings, this work offers a new way to control the final outcome. (Image and research credit: &lt;a href=""&gt;E. Jambon-Puillet&lt;/a&gt;, &lt;a href=""&gt;source&lt;/a&gt;)&lt;/p&gt;</description><link></link><guid></guid><pubDate>Fri, 26 Apr 2019 10:00:13 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>freezing</category><category>evaporation</category><category>sublimation</category><category>coffee rings</category></item><item><title>Subsonic turbulence – like the random and chaotic motions...</title><description>&lt;img src=""/&gt;&lt;br/&gt;&lt;br/&gt;&lt;p&gt;Subsonic &lt;a href=""&gt;turbulence&lt;/a&gt; – like the random and chaotic motions of air and water in our everyday lives – is something we have only a limited understanding of. Our knowledge of supersonic turbulence, where &lt;a href=""&gt;shock waves&lt;/a&gt; and compressibility rule, is even more tenuous. In part this is because, although we can observe snapshots of supersonic turbulence in &lt;a href=""&gt;astronomical&lt;/a&gt; settings like the Orion Nebula shown above, we cannot watch it evolve. On these scales, features simply don’t change appreciably on human timescales. &lt;/p&gt;&lt;p&gt;This has limited scientists to mostly numerical and theoretical studies of supersonic turbulence, but that is starting to change. Researchers are now building &lt;a href=""&gt;experimental set-ups that collide laser-driven plasma jets&lt;/a&gt; to generate boundary-free turbulence at Mach 6. Thus far, the observations are consistent with what’s been seen in nature: at low speeds, the turbulence is consistent with &lt;a href=""&gt;Kolmogorov’s theories&lt;/a&gt;, with energy cascading from large scales to smaller ones predictably. But as the Mach number increases, the nature of the turbulence shifts, moving toward the large density fluctuations seen in nebulae and other astrophysical realms. (Image credit: F. Battistella; research credit: &lt;a href=""&gt;T. White et al.&lt;/a&gt;; see also &lt;a href=""&gt;Nature Astronomy&lt;/a&gt;; submitted by &lt;a href=""&gt;Kam-Yung Soh&lt;/a&gt;)&lt;/p&gt;</description><link></link><guid></guid><pubDate>Thu, 25 Apr 2019 10:00:06 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>astrophysics</category><category>astronomy</category><category>sciblr</category><category>plasma</category><category>magnetohydrodynamics</category><category>shockwave</category><category>supersonic</category><category>turbulence</category><category>supersonic turbulence</category><category>experimental fluid dynamics</category></item><item><title>For many engineering students, their first experience with flow...</title><description>&lt;iframe width="400" height="225"  id="youtube_iframe" src=";enablejsapi=1&amp;origin=;wmode=opaque" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen&gt;&lt;/iframe&gt;&lt;br/&gt;&lt;br/&gt;&lt;p&gt;For many engineering students, their first experience with &lt;a href=""&gt;flow visualization&lt;/a&gt; comes in undergraduate labs, where dye introduced into a flume demonstrates basic flow features around airfoils, cylinders, and spheres. This short video by undergraduate Nick Di Guigno and partners quietly illustrates that experience, from the introduction to the equipment to loading the dye and watching the flow develop under the commentary of one’s professor. For those of you who have done this, I suspect it may ignite a bit of nostalgia. For those who haven’t, I think it captures some of the magical feeling of stepping into the lab the first time, even when you’re just recreating a phenomenon others have seen a thousand times before. (Image and video credit: N. Di Guigno et al.)&lt;/p&gt;&lt;figure data-orig-width="540" data-orig-height="224" class="tmblr-full"&gt;&lt;img src="" alt="image" data-orig-width="540" data-orig-height="224"/&gt;&lt;/figure&gt;</description><link></link><guid></guid><pubDate>Wed, 24 Apr 2019 10:00:07 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>flow visualization</category><category>fluids as art</category></item><item><title>The movement of glaciers is driven by gravity. The immense...</title><description>&lt;img src=""/&gt;&lt;br/&gt;&lt;br/&gt;&lt;p&gt;The movement of &lt;a href=""&gt;glaciers&lt;/a&gt; is driven by gravity. The immense weight of the ice causes it to both slide downhill and deform – or creep. As glacier melting speeds up, scientists have debated how glacier flow will respond: will the loss of ice cause the glaciers to move more slowly since they have less mass, or will the increase in meltwater help lubricate the underside of glaciers and make them flow even faster? &lt;/p&gt;&lt;p&gt;By analyzing satellite image data of Asian glaciers collected between 1985 and 2017, researchers are finally answering that question. &lt;a href=""&gt;Their research&lt;/a&gt; shows that these glaciers are slowing down as they lose mass and speeding up as they gain mass. Nearly all – 94% – of the flow changes they observed can be accounted for solely from ice thickness and slope. This is valuable information as scientists continue to monitor and predict the changes we must expect as the world continues to warm. (Image credit: J. Stevens; research credit: &lt;a href=""&gt;A. Dehecq et al.&lt;/a&gt;; via &lt;a href=""&gt;NASA Earth Observatory&lt;/a&gt;)&lt;/p&gt;</description><link></link><guid></guid><pubDate>Tue, 23 Apr 2019 10:00:27 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>glacier</category><category>glaciology</category><category>ice</category></item></channel></rss>

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