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<rss xmlns:dc="http://purl.org/dc/elements/1.1/" 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!
</description><title>FYFD</title><generator>Tumblr (3.0; @fuckyeahfluiddynamics)</generator><link>https://fyfluiddynamics.com/</link><item><title>A winter bloom of phytoplankton appears as green and teal swirls...</title><description><img src="https://66.media.tumblr.com/09b979b07f9c31517e94acdbfebd5365/tumblr_p6kg68roza1qckzoqo1_500.jpg"/> A winter bloom of <a href="http://fyfluiddynamics.com/tagged/phytoplankton">phytoplankton</a> appears as green and teal swirls in this false-color satellite image of the Gulf of Aden. Although phytoplankton can be an important food source for fish and other marine animals, in recent years we’ve observed more frequent toxic blooms. Currently, physical sampling of the phytoplankton is necessary to determine what type they are, but scientists are working to use multi-spectral imaging to identify different species remotely. As harmful as they can be, blooms like these help <a href="http://fyfluiddynamics.com/tagged/flow+visualization">visualize the flow</a> and mixing in different coastal regions. Here, for example, we can see distinctive <a href="http://fyfluiddynamics.com/tagged/turbulent+eddies">turbulent eddies</a> in the Gulf that are tens of kilometers across. (Image credit: N. Kuring/NASA; via <a href="https://earthobservatory.nasa.gov/IOTD/view.php?id=91937">NASA Earth Observatory</a>)</description><link>https://fyfluiddynamics.com/post/186469639959</link><guid>https://fyfluiddynamics.com/post/186469639959</guid><pubDate>Mon, 22 Jul 2019 10:00:30 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>flow visualization</category><category>phytoplankton</category><category>turbulence</category></item><item><title>We can’t always see the flows around us, but that doesn’t mean...</title><description><img src="https://66.media.tumblr.com/ce48e8f2255dfdb04bf9d032c1d92cd6/tumblr_puumm9FbCk1qckzoqo1_500.png"/> We can’t always see the flows around us, but that doesn’t mean they’re not there. Audobon Photography Award winner Kathrin Swaboda waited for a cold morning to catch this spectacular photo of a red-winged blackbird’s song. In the morning chill, moisture from the bird’s breath condensed inside the vortex rings it emitted, giving us a glimpse of its sound. (Image credit: <a href="https://kathrinswobodaphotography.com/">K. Swaboda</a>; via <a href="https://gizmodo.com/a-blackbird-blowing-smoke-rings-wins-top-prize-at-the-2-1836308346">Gizmodo</a>; submitted by <a href="https://twitter.com/jpshoer/status/1149754474639921152">Joseph S</a> and <a href="https://twitter.com/lifeaquatic/status/1149639863349596161">Stuart H</a>)</description><link>https://fyfluiddynamics.com/post/186400156909</link><guid>https://fyfluiddynamics.com/post/186400156909</guid><pubDate>Fri, 19 Jul 2019 10:00:04 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>biology</category><category>sciblr</category><category>condensation</category><category>acoustics</category><category>birds</category><category>vortex rings</category><category>fluids as art</category></item><item><title>Citrus fruits like oranges house tiny pockets of oil in their...</title><description><img src="https://66.media.tumblr.com/327b8f33cfde13702dc458f40a48e9ae/tumblr_pjmxfwlvlG1qckzoqo1_500.gif"/> Citrus fruits like oranges house tiny pockets of oil in their peels. When squeezed, the oils jet out in tiny micro-jets that are about the width of a human hair. Despite their small size, the jets reach speeds of about 30 m/s and quickly break into a stream of droplets. When exposed to the flame of a lighter, like in the animation above, those microdroplets <a href="http://fyfluiddynamics.com/tagged/combustion">combust</a> easily, creating a momentary fireball used to augment some cocktails. For more on how the citrus peel generates these jets, check out <a href="https://fyfluiddynamics.com/post/184919630606/bartenders-and-citrus-lovers-the-world-over-are">this previous post</a>. (Image credit: <a href="https://www.youtube.com/channel/UCFH4dWqQQOYkyJZUGT4q5pg/videos">Warped Perception</a>, <a href="https://www.youtube.com/watch?v=m8LOaBt_FSg">source</a>; research credit: <a href="https://doi.org/10.1073/pnas.1720809115">N. Smith et al.</a>)</description><link>https://fyfluiddynamics.com/post/186376690014</link><guid>https://fyfluiddynamics.com/post/186376690014</guid><pubDate>Thu, 18 Jul 2019 10:00:07 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>biology</category><category>sciblr</category><category>citrus</category><category>microfluidics</category><category>jet</category><category>combustion</category></item><item><title>As anyone who’s jumped off the high board can tell you, hitting...</title><description><iframe width="400" height="225" id="youtube_iframe" src="https://www.youtube.com/embed/Rr2Pk_ILSjk?feature=oembed&enablejsapi=1&origin=https://safe.txmblr.com&wmode=opaque" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe> As anyone who’s jumped off the high board can tell you, hitting the water involves a lot of force. That’s because any solid object entering the water has to accelerate water out of its way. This is why <a href="https://fyfluiddynamics.com/post/165583528619/one-of-my-favorite-things-to-do-while-we-were">gannets and other diving birds streamline themselves</a> before entering the water. But even for non-streamlined objects, like a sphere, there are ways to reduce the force of impact.This video explores three such techniques, all of which involve disturbing the water before the sphere enters. In the first, the sphere is dropped inside a jet of fluid. Since the jet is already forcing water down and aside when the sphere enters, the acceleration provided by the sphere is less and so is the force it experiences.The second and third techniques both rely on dropping a solid object ahead of the one we care about. In the second case, a smaller sphere breaks the surface ahead of the larger one, allowing the big sphere to hit a cavity rather than an undisturbed surface. Like with the jet, the first sphere’s entry has already accelerated fluid downward, so there’s less mass that the bigger sphere has to accelerate, thereby reducing its impact force.In the third case, the first sphere is dropped well ahead of the second, creating an upward-moving <a href="https://fyfluiddynamics.com/tagged/Worthington+jet">Worthington jet</a> that the second sphere hits. In this case, there’s water moving upward into the sphere, so how could this possibly reduce the force of entry? The key here is that the water of the jet wets the sphere before it enters the pool. Notice how very little air accompanies the second sphere compared to the first one. That’s because the second sphere is already wet. It’s also been slowed down by the jet so that it enters the water at a lower speed, all of which adds up to a lower force of entry. (Image and research credit: <a href="https://doi.org/10.1103/APS.DFD.2018.GFM.V0088">N. Speirs et al.</a>)<figure data-orig-width="540" data-orig-height="304" class="tmblr-full"><img src="https://66.media.tumblr.com/485e2ccb98e9ae88924236ae540f7169/tumblr_inline_psw4ywNGO91qzrgfe_540.gif" alt="image" data-orig-width="540" data-orig-height="304"/></figure></description><link>https://fyfluiddynamics.com/post/186353488324</link><guid>https://fyfluiddynamics.com/post/186353488324</guid><pubDate>Wed, 17 Jul 2019 10:00:23 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>2018gofm</category><category>splashes</category><category>water entry</category><category>diving</category><category>jets</category><category>Worthington jet</category><category>cavity</category><category>wetting</category></item><item><title>Not everything that behaves like a fluid is a liquid or a gas....</title><description><iframe width="400" height="225" id="youtube_iframe" src="https://www.youtube.com/embed/dU2rLhpaMAY?feature=oembed&enablejsapi=1&origin=https://safe.txmblr.com&wmode=opaque" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe> Not everything that behaves like a fluid is a liquid or a gas. In particular, groups of organisms can behave in a collective manner that is remarkably flow-like. From <a href="https://fyfluiddynamics.com/post/182373799896/herds-flocks-schools-and-even-crowds-can-behave">schools of fish</a> to <a href="https://fyfluiddynamics.com/post/164024491802/substances-dont-have-to-be-a-liquid-or-a-gas-to">fire-ant rafts</a>, nature is full of examples of groups with fluid-like properties. One of the most mesmerizing examples are these giant honeybee colonies, which essentially <a href="http://fyfluiddynamics.com/post/182451009233/giant-honeybees-live-in-huge-open-nests-to">do “the wave” to frighten away predators</a> like wasps. Researchers are still trying to understand and mimic the way these groups coordinate such behaviors. Can even complicated patterns be generated by a simple set of rules an individual animal follows? That’s the sort of question <a href="https://fyfluiddynamics.com/tagged/active+matter">active matter</a> researchers investigate. Check out the video above to see a whole cliff’s worth of bee colonies shimmering. (Image and video credit: BBC Earth)<figure data-orig-width="540" data-orig-height="304" class="tmblr-full"><img src="https://66.media.tumblr.com/dcef101abd1c2bec931893aab4b3d72d/tumblr_inline_psxy76AKHx1qzrgfe_540.gif" alt="image" data-orig-width="540" data-orig-height="304"/></figure></description><link>https://fyfluiddynamics.com/post/186329540924</link><guid>https://fyfluiddynamics.com/post/186329540924</guid><pubDate>Tue, 16 Jul 2019 10:00:26 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>biology</category><category>bees</category><category>collective motion</category><category>active matter</category><category>waves</category></item><item><title>Living near the Rocky Mountains, it’s not unusual to look up and...</title><description><img src="https://66.media.tumblr.com/e8b6b24b78c5b39b866129671dcba21c/tumblr_ptrmks3hSP1qckzoqo1_500.jpg"/> Living near the Rocky Mountains, it’s not unusual to look up and find the sky striped with lines of clouds. Such wave clouds are often formed <a href="https://fyfluiddynamics.com/post/173030824979/stripe-like-wave-clouds-can-often-form-downstream">on the lee side of mountains</a> and other topography. But even in the flattest plains, you can find clouds like these at times. That’s because the <a href="https://fyfluiddynamics.com/tagged/internal+waves">internal waves</a> necessary to create the clouds can be generated by weather fronts, too.Imagine a bit of atmosphere sitting between a low-pressure zone and a high-pressure zone. This will be an area of <a href="https://en.wikipedia.org/wiki/Convergence_zone">convergence</a>, where winds flow inward and squeeze the fluid parcel in one direction before turning 90 degrees and stretching it in the perpendicular direction. The result is a sharpening of any temperature gradient along the interface. This is the weather front that moves in and causes massive and sudden shifts in temperature. On one side of the front, warm air rises. Then, as it loses heat and cools, it sinks down the cold side of the front. The sharper the temperature differences become, the stronger this circulation gets. If the air is vertically displaced quickly enough, it will spontaneously generate waves in the atmosphere. With the right moisture conditions, those waves create visible clouds at their crests, as seen here. For more on the process, check out <a href="https://physicstoday.scitation.org/doi/10.1063/PT.3.4225">this article over at Physics Today</a>. (Image credit: <a href="https://www.pexels.com/photo/photography-of-clouds-844112/">W. Velasquez</a>; via <a href="https://physicstoday.scitation.org/doi/10.1063/PT.3.4225">Physics Today</a>)</description><link>https://fyfluiddynamics.com/post/186305589144</link><guid>https://fyfluiddynamics.com/post/186305589144</guid><pubDate>Mon, 15 Jul 2019 10:00:15 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>meteorology</category><category>atmospheric science</category><category>sciblr</category><category>weather</category><category>clouds</category><category>wave clouds</category><category>internal waves</category><category>convection</category><category>circulation</category></item><item><title>On a hot day, it’s not unusual to catch a glimpse of a...</title><description><img src="https://66.media.tumblr.com/bac4ca64646f57e667f1693309d6ffc4/tumblr_ppr6g8v5iP1qckzoqo1_500.gif"/> On a hot day, it’s not unusual to catch a glimpse of a shimmering <a href="http://fyfluiddynamics.com/tagged/optical+illusion">optical illusion</a> over a hot road, but you probably wouldn’t expect to see the same thing 2,000 meters under the ocean. Yet that’s exactly what a team of scientists saw through the cameras of their unmanned submersible as it explored hydrothermal vents deep in the Pacific Ocean.At these depths, the pressure is high enough that water can reach more than 350 degrees Celsius without boiling. The hot fluid from the vents rises and gets caught beneath mineral overhangs, forming a sort of upside-down pool. Since the <a href="https://en.wikipedia.org/wiki/Refractive_index">index of refraction</a> of the hot water is different than that of the colder surrounding water, we see a mirror-like surface at some viewing angles. Be sure to check out the whole video for more examples of the illusion. (Image and video credit: Schmidt Ocean; via <a href="https://www.smithsonianmag.com/science-nature/scientists-spot-beautiful-optical-illusion-bottom-sea-180971902/?utm_source=twitter.com&utm_medium=socialmedia">Smithsonian</a>; submitted by <a href="https://twitter.com/sohkamyung/status/1115418792165699584">Kam-Yung Soh</a>)<figure class="tmblr-embed tmblr-full" data-provider="youtube" data-orig-width="540" data-orig-height="304" data-url="https%3A%2F%2Fyoutu.be%2FnyzOFseY8p0"><iframe width="540" height="304" id="youtube_iframe" src="https://www.youtube.com/embed/nyzOFseY8p0?feature=oembed&enablejsapi=1&origin=https://safe.txmblr.com&wmode=opaque" frameborder="0" allowfullscreen="allowfullscreen"></iframe></figure></description><link>https://fyfluiddynamics.com/post/186235701823</link><guid>https://fyfluiddynamics.com/post/186235701823</guid><pubDate>Fri, 12 Jul 2019 10:00:15 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>oceanography</category><category>sciblr</category><category>optical illusion</category><category>optics</category><category>refraction</category></item><item><title>In “Aurora”, artist Rus Khasanov uses fluids to create a short...</title><description><iframe src="https://player.vimeo.com/video/333521780?title=0&byline=0&portrait=0&app_id=122963" width="400" height="225" frameborder="0" title="A U R O R A" allow="autoplay; fullscreen" allowfullscreen></iframe> In “<a href="https://www.behance.net/gallery/79632513/A-U-R-O-R-A">Aurora</a>”, artist <a href="https://www.instagram.com/ruskhasanov">Rus Khasanov</a> uses fluids to create a short film full of psychedelic color and cosmic visuals. As in a soap bubble, the bright colors – as well as the pure black holes – come from the <a href="https://fyfluiddynamics.com/post/53441085783/the-brilliant-and-beautiful-colors-of-a-bubble-are">interference of light rays</a>. The colors directly relate to the thickness of fluid, and they allow us to see all the subtle flows caused by <a href="https://fyfluiddynamics.com/tagged/Marangoni+effect">variations in surface tension</a>. (Video and image credit: R. Khasanov)<figure data-orig-width="1400" data-orig-height="934" class="tmblr-full"><img src="https://66.media.tumblr.com/eff9f445421106b19000029ae8bba909/tumblr_inline_pr74irVgfi1qzrgfe_540.jpg" alt="image" data-orig-width="1400" data-orig-height="934"/></figure><figure data-orig-width="600" data-orig-height="338" class="tmblr-full"><img src="https://66.media.tumblr.com/4d8eab4d12a93f76bd2319df135407d4/tumblr_inline_pr74itNqHp1qzrgfe_540.gif" alt="image" data-orig-width="600" data-orig-height="338"/></figure><figure data-orig-width="1400" data-orig-height="934" class="tmblr-full"><img src="https://66.media.tumblr.com/ea2f0e8c839b121001ac888792295846/tumblr_inline_pr74irF44d1qzrgfe_540.jpg" alt="image" data-orig-width="1400" data-orig-height="934"/></figure></description><link>https://fyfluiddynamics.com/post/186212199788</link><guid>https://fyfluiddynamics.com/post/186212199788</guid><pubDate>Thu, 11 Jul 2019 10:00:06 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>fluids as art</category><category>interference</category><category>flow visualization</category><category>surface tension</category><category>Marangoni effect</category></item><item><title>Soft systems like this bubble raft can retain memory of how they...</title><description><img src="https://66.media.tumblr.com/981fe55415d65efc3058038d2117888e/tumblr_ps82yhJldY1qckzoqo1_400.gif"/> Soft systems like this bubble raft can retain memory of how they reached their current configuration. Because the bubbles are different sizes, they cannot pack into a crystalline structure, and because they’re too close together to move easily, they cannot reconfigure into their most efficient packing. This leaves the system out of equilibrium, which is key to its memory. By shearing the bubbles between a spinning inner ring (left in image) and a stationary outer one (not shown) several times, <a href="https://doi.org/10.1103/PhysRevLett.122.158001">researchers found they they could coax the bubbles</a> into a configuration that was unresponsive to further shearing at that amplitude. Once the bubbles were configured, the scientists could sweep through many shear amplitudes and look for the one with the smallest response. This was always the “remembered” shear amplitude. Effectively, the system can record and read out values similar to the way a computer bit does. Bubbles are no replacement for silicon, though. In this case, scientists are more interested in what memory in these systems can teach us about other, similar mechanical systems and how they respond to forces. (Image and research credit: <a href="https://doi.org/10.1103/PhysRevLett.122.158001">S. Mukherji et al.</a>; via <a href="https://physicstoday.scitation.org/do/10.1063/PT.6.1.20190523a/full/">Physics Today</a>; submitted by <a href="https://twitter.com/sohkamyung/status/1131744550337146881">Kam-Yung Soh</a>)</description><link>https://fyfluiddynamics.com/post/186188737222</link><guid>https://fyfluiddynamics.com/post/186188737222</guid><pubDate>Wed, 10 Jul 2019 10:00:05 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>bubbles</category><category>shear</category><category>soft matter</category><category>Taylor-Couette flow</category><category>jamming</category></item><item><title>Periodically, our sun releases plasma in a coronal mass...</title><description><img src="https://66.media.tumblr.com/3f46e07f3c131a89e5864c67c4b1a65e/tumblr_ptewdiNgfu1qckzoqo1_500.gif"/> Periodically, our <a href="https://fyfluiddynamics.com/tagged/sun">sun</a> releases plasma in a coronal mass ejection. Afterwards, the local magnetic field lines shift and reorganize. We can see that process in action here because charged particles spin along the magnetic lines, outlining them as bright loops in this imagery. This sequence – one of the best examples of this phenomenon to date – was captured by NASA’s Solar Dynamics Observatory in early 2017. To understand behaviors like these, scientists use <a href="https://fyfluiddynamics.com/tagged/magnetohydrodynamics">magnetohydrodynamics</a>, a marriage of the equations of fluid mechanics with Maxwell’s equations for electromagnetism. (Image credit: NASA SDO, <a href="https://photojournal.jpl.nasa.gov/catalog/PIA21598">source</a>)</description><link>https://fyfluiddynamics.com/post/186165316904</link><guid>https://fyfluiddynamics.com/post/186165316904</guid><pubDate>Tue, 09 Jul 2019 10:00:24 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>astrophysics</category><category>sun</category><category>plasma</category><category>magnetic field</category><category>flow visualization</category><category>magnetohydrodynamics</category><category>NASA SDO</category></item><item><title>Drops that impact a very hot surface will surf on their own...</title><description><img src="https://66.media.tumblr.com/5f39e649ebc8cc0efa94990dc8d52e70/tumblr_prlu9mDRqa1qckzoqo1_500.gif"/> Drops that impact a very hot surface will <a href="https://fyfluiddynamics.com/tagged/Leidenfrost+drops">surf on their own vapor</a>, and ones that hit a very cold surface will <a href="https://fyfluiddynamics.com/post/183542351453/at-the-altitudes-where-aircraft-fly-its-often">freeze almost immediately</a>. But what happens when the temperature differences aren’t so extreme? Scientists explored this (above) by dropping room-temperature water droplets onto a cool surface – one warmer than the freezing point but cooler than the dew point at which water condenses. They found that impacting drops formed a triple halo of condensate (right). The first and brightest ring forms at the radius of the drop’s maximum extent during impact. The second band forms from water vapor that leaves the droplet at impact. As that vapor cools, it condenses into a second band. The final, dimmest band forms as the droplet stabilizes and cools. It’s the result of water vapor near the droplet continuing to cool and condense. (Image and research credit: <a href="https://doi.org/10.1063/1.5080356">Y. Zhao et al.</a>; via <a href="https://www.nature.com/articles/d41586-019-01538-3">Nature News</a>; submitted by <a href="https://twitter.com/sohkamyung/status/1128460695161327616">Kam-Yung Soh</a>)</description><link>https://fyfluiddynamics.com/post/186141683384</link><guid>https://fyfluiddynamics.com/post/186141683384</guid><pubDate>Mon, 08 Jul 2019 10:00:28 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>droplet impact</category><category>condensation</category></item><item><title>Most of us have probably never given much thought to how a fire...</title><description><iframe width="400" height="225" id="youtube_iframe" src="https://www.youtube.com/embed/NXAgjKDFc14?feature=oembed&enablejsapi=1&origin=https://safe.txmblr.com&wmode=opaque" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe> Most of us have probably never given much thought to how a fire sprinkler works, but fortunately, the Slow Mo Guys have used their high-speed skills to answer that question anyway. Sprinkler systems of this variety are constantly pressurized by a full pipe line of water that’s held back by a thin metal disk and a colored glass ampule containing a fluid like alcohol. The color of ampule indicates the <a href="https://en.wikipedia.org/wiki/Fire_sprinkler_system#/media/File:Sprinkler_glass_bulbs.svg">temperature at which the system is designed to activate</a>. As the ampule heats up, the fluid inside expands, breaking the ampule at or near the critical temperature. That allows the metal disk to fall away and releases a torrent of water, which falls onto the gear-like disk at the bottom of the sprinkler and gets flung out over a wider area. Despite appearances, that bottom disk is stationary, not spinning; its shape alone is what distributes the water. (Image and video credit: The Slow Mo Guys)<figure data-orig-width="540" data-orig-height="300" class="tmblr-full"><img src="https://66.media.tumblr.com/976e1ed54453103be27c88ff2e49a1f6/tumblr_inline_pr4ws5VDEz1qzrgfe_540.gif" alt="image" data-orig-width="540" data-orig-height="300"/></figure></description><link>https://fyfluiddynamics.com/post/186072179628</link><guid>https://fyfluiddynamics.com/post/186072179628</guid><pubDate>Fri, 05 Jul 2019 10:00:11 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>engineering</category><category>fire suppression system</category><category>fire sprinkler</category><category>high-speed video</category></item><item><title>Not long ago, we learned for the first time that dandelion seeds...</title><description><img src="https://66.media.tumblr.com/69aba254e8155d31a2925aebbeeca8f7/tumblr_pu2rb0SLxY1qckzoqo1_500.jpg"/> <img src="https://66.media.tumblr.com/db8721fca4a0b8035ecff730e38fca6c/tumblr_pu2rb0SLxY1qckzoqo2_r1_500.png"/> <a href="https://fyfluiddynamics.com/post/184849874583/to-kick-off-plant-week-here-on-fyfd-were-taking">Not long ago</a>, we learned for the first time that dandelion seeds fly thanks to a stable separated vortex ring that sits behind their bristly pappus. Building on that work, researchers have now <a href="https://doi.org/10.1103/PhysRevFluids.4.071901">published a mathematical analysis</a> of flow around a simplified dandelion pappus. Despite their simplifications, the model captures the flow observed in the previous experiments (bottom image: experiments on left; model on right). The model also allowed researchers to test various features – like the number of filaments in the pappus – and see how they affected the flow. Interestingly, they found that dandelion flight was most stable with about 100 filaments, which is right around the number of a typical pappus! (Image credits: dandelion - <a href="https://www.pexels.com/photo/blossom-blur-close-up-dandelion-289323/">Pixabay</a>, figure - <a href="https://doi.org/10.1103/PhysRevFluids.4.071901">P. Ledda et al.</a>; research credit: <a href="https://doi.org/10.1103/PhysRevFluids.4.071901">P. Ledda et al.</a>; via <a href="https://physics.aps.org/synopsis-for/10.1103/PhysRevFluids.4.071901">APS Physics</a>; submitted by Kam-Yung Soh and Marc A.)</description><link>https://fyfluiddynamics.com/post/186049744063</link><guid>https://fyfluiddynamics.com/post/186049744063</guid><pubDate>Thu, 04 Jul 2019 10:00:10 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>biology</category><category>parachutes</category><category>dandelion</category><category>gliding</category><category>aerodynamics</category><category>vortex ring</category><category>separated vortex ring</category><category>plants</category><category>porosity</category><category>drag generation</category></item><item><title>Earth’s earlier ages are filled with enduring mysteries about...</title><description><img src="https://66.media.tumblr.com/4bad54a256d65e481de3943ccd66c70e/tumblr_ptm2okUE1d1qckzoqo1_500.png"/> <img src="https://66.media.tumblr.com/ba6db242bdbc79e02936d187bdf2ede5/tumblr_ptm2okUE1d1qckzoqo2_500.png"/> Earth’s earlier ages are filled with enduring mysteries about the plants and creatures that lived and died long before humanity. Many of <a href="https://fyfluiddynamics.com/tagged/paleontology">these organisms</a>, like the aquatic Ernietta shown above, are known only from scattered fossil remains. Yet fluid dynamics is helping us understand how Ernietta lived and fed some 545 million years ago.Ernietta were sack-like organisms consisting of stitched-together tubular elements. They had no way to move around and no obvious method for transporting nutrients into their bodies. Scientists hypothesized that they likely used one of two feeding methods: either Ernietta relied on its surface area to <a href="https://fyfluiddynamics.com/tagged/diffusion">extract nutrients directly</a> from the water or its shape enabled it to trap larger particles to feed on from the flow. To decide between these modes, scientists turned to <a href="https://fyfluiddynamics.com/tagged/computational+fluid+dynamics">computational fluid dynamics</a>.By modelling both single Ernietta and small groups, they found that the shape of the organism generates a rotating current inside the bag that pulls flow down along one side and back up the other. Moreover, being near one another enhanced this effect, helping downstream Ernietta catch more particles than they otherwise would. All in all, the results suggest not only Ernietta’s likely feeding method but also that they lived in colonies and practiced one of the earliest known examples of communal feeding! (Image credit: D. Mazierski, <a href="https://arstechnica.com/science/2019/06/physics-indicates-some-of-earths-earliest-animals-helped-each-other-feed/">source</a>; research credit: <a href="https://advances.sciencemag.org/content/5/6/eaaw0260">B. Gibson et al.</a>; via <a href="https://arstechnica.com/science/2019/06/physics-indicates-some-of-earths-earliest-animals-helped-each-other-feed/">ArsTechnica</a>; submitted by <a href="https://twitter.com/sohkamyung/status/1142965645346164736">Kam-Yung Soh</a>)</description><link>https://fyfluiddynamics.com/post/186025957280</link><guid>https://fyfluiddynamics.com/post/186025957280</guid><pubDate>Wed, 03 Jul 2019 10:00:01 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>biology</category><category>paleontology</category><category>sciblr</category><category>suspension feeding</category><category>computational fluid dynamics</category><category>CFD</category><category>numerical simulation</category></item><item><title>Last week, NASA announced its next New Frontiers mission: a...</title><description><img src="https://66.media.tumblr.com/e648b93ed70c1853139d9212f09da341/tumblr_ptyxosWPQx1qckzoqo1_500.jpg"/> Last week, NASA announced its next New Frontiers mission: a nuclear-powered drone named Dragonfly heading to <a href="https://fyfluiddynamics.com/tagged/titan">Titan</a>. This astrobiology mission is set to search our solar system’s second largest moon for signs of life. It’s exciting aerodynamically, as well, since Titan’s thick atmosphere makes it uniquely suited for heavier-than-air flight. Therefore, rather than using wheeled rovers like we have on Mars, Dragonfly is a rotorcraft. It will be capable of traveling up to 8km per flight, which will quickly surpass the fewer than 21km the Curiosity Rover has managed on Mars! Like Earth, Titan has rainfall and <a href="https://fyfluiddynamics.com/post/158628839456/titan-saturns-largest-moon-is-a-fascinating">open liquid bodies</a> on its surface. I, for one, can’t wait to see the alien vistas Dragonfly sends back as it cruises over methane lakes. (Image and video credit: NASA)<figure class="tmblr-embed tmblr-full" data-provider="youtube" data-orig-width="540" data-orig-height="304" data-url="https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3Dxn3-0a19sC8"><iframe width="540" height="304" id="youtube_iframe" src="https://www.youtube.com/embed/xn3-0a19sC8?feature=oembed&enablejsapi=1&origin=https://safe.txmblr.com&wmode=opaque" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen=""></iframe></figure></description><link>https://fyfluiddynamics.com/post/186002562793</link><guid>https://fyfluiddynamics.com/post/186002562793</guid><pubDate>Tue, 02 Jul 2019 10:00:18 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>planetary science</category><category>aerodynamics</category><category>rotorcraft</category><category>NASA</category><category>sciblr</category><category>Dragonfly</category></item><item><title>Take a mixture of a viscous liquid – like clay mud –...</title><description><img src="https://66.media.tumblr.com/064d13e3aa7ea2b7f02af87733d93a01/tumblr_pqqfefWrWv1qckzoqo1_500.gif"/> Take a mixture of a viscous liquid – like clay mud – and squeeze it between two glass plates and you’ll create a mostly-round layer of liquid. As you pry the two glass plates apart, air will push its way into that layer, forcing through the mud in a dendritic pattern. This is called the <a href="https://en.wikipedia.org/wiki/Saffman%E2%80%93Taylor_instability">Saffman-Taylor instability</a> or <a href="https://fyfluiddynamics.com/tagged/viscous+fingering">viscous fingering</a>. It occurs because the interface between the air and mud is unstable. (Image and video credit: <a href="https://t.umblr.com/redirect?z=https%3A%2F%2Fvimeo.com%2Fatelieramaco&t=NjNiZTY0ZGE3MWNlNjRiM2VmZWI1NzIxMjJkNDhkZDU4MWRiODk1ZSxudWJGaXRaNA%3D%3D&b=t%3AEpT9D-ko1A7dI_sOVcsSQQ&p=https%3A%2F%2Ffyfluiddynamics.com%2Fpost%2F171348007234%2Fif-you-try-to-build-a-pyramid-of-dry-glass-beads&m=0">amàco</a> et al.)<figure class="tmblr-embed tmblr-full" data-provider="vimeo" data-orig-width="540" data-orig-height="304" data-url="https%3A%2F%2Fvimeo.com%2F175698030"><iframe src="https://player.vimeo.com/video/175698030?title=0&byline=0&portrait=0&app_id=122963" width="540" height="304" frameborder="0" title="Fingers of air in clay mud" allowfullscreen="allowfullscreen"></iframe></figure></description><link>https://fyfluiddynamics.com/post/185978837156</link><guid>https://fyfluiddynamics.com/post/185978837156</guid><pubDate>Mon, 01 Jul 2019 10:00:24 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>Saffman-Taylor instability</category><category>viscous fingering</category><category>fluids as art</category><category>instability</category><category>viscous flow</category></item><item><title>Although Thomas Blanchard’s latest short film, “-N- Uprising”,...</title><description><iframe src="https://player.vimeo.com/video/343068761?title=0&byline=0&portrait=0&app_id=122963" width="400" height="225" frameborder="0" title="-N- Uprising HDR" allow="autoplay; fullscreen" allowfullscreen></iframe> Although Thomas Blanchard’s latest short film, <a href="https://vimeo.com/343068761">“-N- Uprising”</a>, is less overtly fluid dynamical, fluids underlie almost every aspect of it. The blossoming of flowers is often <a href="https://fyfluiddynamics.com/post/131157479125/though-most-plants-dont-move-at-speeds-that-we">driven by osmosis and water pressure</a>. Spiders <a href="https://fyfluiddynamics.com/post/179622310544/theres-something-about-the-way-spiders-move-that">rely on hydraulic pressure</a> to move their limbs, and many insects first <a href="https://meetings.aps.org/Meeting/MAR19/Session/K57.11">unfurl their wings by pumping hemolymph</a> through the network of veins that lace them. Even when hidden beneath the surface, fluid dynamics is everywhere. (Video credit: T. Blanchard; via <a href="https://www.thisiscolossal.com/2019/06/n-uprising-thomas-blanchard/">Colossal</a>)<figure data-orig-width="540" data-orig-height="282" class="tmblr-full"><img src="https://66.media.tumblr.com/d6bfb6c760a4d754d604c0c2d303f90e/tumblr_inline_ptpsacd2Hl1qzrgfe_540.gif" alt="image" data-orig-width="540" data-orig-height="282"/></figure><figure data-orig-width="540" data-orig-height="284" class="tmblr-full"><img src="https://66.media.tumblr.com/1bf02e55f5c7dff52158ccec3ff245dd/tumblr_inline_ptpsa8Jk1u1qzrgfe_540.gif" alt="image" data-orig-width="540" data-orig-height="284"/></figure><figure data-orig-width="540" data-orig-height="282" class="tmblr-full"><img src="https://66.media.tumblr.com/4209271103d07933de586fe1c489c6e1/tumblr_inline_ptpsa7Ex8U1qzrgfe_540.gif" alt="image" data-orig-width="540" data-orig-height="282"/></figure></description><link>https://fyfluiddynamics.com/post/185909862334</link><guid>https://fyfluiddynamics.com/post/185909862334</guid><pubDate>Fri, 28 Jun 2019 10:00:15 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>biology</category><category>sciblr</category><category>fluids as art</category><category>plants</category><category>freezing</category><category>insects</category><category>hydraulic pressure</category></item><item><title>As the climate warms, many urban centers are facing stronger and...</title><description><img src="https://66.media.tumblr.com/c619b461efa53828832c4ccdf59e6259/tumblr_pqsa5tCvQo1qckzoqo1_500.gif"/> As the climate warms, many urban centers are facing stronger and more frequent storms. Some, like New York City, are using <a href="http://fyfluiddynamics.com/tagged/numerical+simulation">numerical simulations</a> to better understand the interactions of their complicated urban geometries with hurricane force winds. Above you see a simulation showing predicted wind speeds in a Lower Eastside neighborhood. The incoming wind speed (from the left) is roughly 60 m/s (~134 mph), but the speeds around and between buildings are as much as 2 times higher than that. That means that, even if a storm is <a href="https://en.wikipedia.org/wiki/Saffir%E2%80%93Simpson_scale">Category 3 or 4</a>, there will be areas of a neighborhood that receive sustained winds well beyond the range of a Category 5 hurricane. Urban planners need this sort of data both for devising building requirements and for understanding what storm conditions warrant mandatory evacuations for residents. (Video and image credit: <a href="https://gfm.aps.org/meetings/dfd-2018/5b9bce25b8ac3105e5ac9075">X. Jiang et al.</a>)<figure class="tmblr-embed tmblr-full" data-provider="youtube" data-orig-width="540" data-orig-height="304" data-url="https%3A%2F%2Fyoutu.be%2F9G3zZzyXuEc"><iframe width="540" height="304" id="youtube_iframe" src="https://www.youtube.com/embed/9G3zZzyXuEc?feature=oembed&enablejsapi=1&origin=https://safe.txmblr.com&wmode=opaque" frameborder="0" allowfullscreen="allowfullscreen"></iframe></figure></description><link>https://fyfluiddynamics.com/post/185886838064</link><guid>https://fyfluiddynamics.com/post/185886838064</guid><pubDate>Thu, 27 Jun 2019 10:00:11 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>meteorology</category><category>climate change</category><category>hurricanes</category><category>sciblr</category><category>numerical simulation</category><category>computational fluid dynamics</category><category>New York City</category><category>les</category><category>Large Eddy simulation</category></item><item><title>Transporting droplets easily and reliably is important in many...</title><description><img src="https://66.media.tumblr.com/3ffc4e58c7c5e1294359e3384bfda336/tumblr_pt976gRro71qckzoqo3_500.gif"/> <img src="https://66.media.tumblr.com/c79f11c7d87b0fa69318a04407408253/tumblr_pt976gRro71qckzoqo1_500.png"/> <img src="https://66.media.tumblr.com/8cc986202d63d5e257c071f5ca912ba4/tumblr_pt976gRro71qckzoqo2_500.gif"/> Transporting droplets easily and reliably is important in many <a href="https://fyfluiddynamics.com/tagged/microfluidics">microfluidic</a> applications. While this can be done using electric fields, those fields can impact biological characteristics researchers are trying to measure. As an alternative, a group of researchers have developed the concept of “mechanowetting,” a technique that uses surface tension forces to hold droplets on a traveling wave.Now visually, it’s a bit tough to see what’s going on here. In the animations, it looks like the droplets are just sticking to a moving surface, but that’s an illusion. The surface the droplet is sitting on is fixed and unmoving. It’s a thin silicone film that covers a ridged conveyor belt. The belt underneath can (and does) move. This creates a traveling wave. Instead of that wave simply passing beneath the droplet, it triggers an internal flow and restoring force that helps the drop follow the wave. The effect is strong enough that small droplets are even able to climb up vertical walls or stick upside-down. (Image, research, and submission credit: <a href="https://advances.sciencemag.org/content/5/6/eaaw0914">E. de Jong et al.</a>)</description><link>https://fyfluiddynamics.com/post/185863861111</link><guid>https://fyfluiddynamics.com/post/185863861111</guid><pubDate>Wed, 26 Jun 2019 10:00:29 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>droplet transport</category><category>microfluidics</category><category>surface tension</category><category>flow visualization</category><category>waves</category></item><item><title>Although many people have studied droplet impacts over the...</title><description><img src="https://66.media.tumblr.com/94959f2bd113b3004b4e580645af01ad/tumblr_pt1pq7RAej1qckzoqo1_500.gif"/> Although many people have studied <a href="https://fyfluiddynamics.com/tagged/droplet+impact">droplet impacts</a> over the years, there’s been remarkably little work done with oil-on-water impacts. One of the things that makes this situation different is that the oil and water are completely <a href="https://fyfluiddynamics.com/tagged/miscibility">immiscible</a>, which means we can see aspects of the impact process that are invisible with, say, water-on-water impacts.The animation above shows an underwater view of the oil droplet’s impact. The energy of the initial impact creates an expanding crater and an unstable <a href="https://fyfluiddynamics.com/tagged/crowning">crown splash</a>. That crown splash contains both water and oil. After it ejects some droplets, the rim stabilizes, but we can still see small perturbations along its edge as it starts to retract. In the water, high surface tension damps out these perturbations. Not so for the oil! As the crater retracts, the small disturbances along the rim get stretched into mushroom-shaped fingers that point inward toward the impact site. Because the index of refraction is different between oil and water, we can see the fingers clearly near the end of the animation. (Image and research credit: <a href="https://pubs.rsc.org/en/content/articlelanding/2019/sm/c9sm00318e">U. Jain et al.</a>; submitted by <a href="https://twitter.com/seriouslynotUJ/status/1138927881080455171">Utkarsh J.</a>)</description><link>https://fyfluiddynamics.com/post/185840789690</link><guid>https://fyfluiddynamics.com/post/185840789690</guid><pubDate>Tue, 25 Jun 2019 10:00:16 -0500</pubDate><category>fluid dynamics</category><category>science</category><category>physics</category><category>sciblr</category><category>droplet impact</category><category>miscibility</category><category>flow visualization</category><category>instability</category><category>cavity</category><category>splashes</category></item></channel></rss>

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