FYFD

Tag: fluids as art

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    “Monsoon IV”

    It’s a cliché to claim that the sky is bigger in the American West, but the wide, open views in that region do offer a very different perspective on weather. Photographer Mike Olbinski’s works give viewers a taste of that perspective of far-off thunderstorms, towering anvil clouds, and massive downpours in the distance. At the same time, many of his sequences illustrate the birth and death of these massive storms. As warm, moist air rises, a puffy cumulus cloud (below) swells upward as fresh moisture condenses. When it reaches a thermal cap and can rise no further, precipitation begins to fall, dragging surrounding air with it. This is the mature stage of a storm, when both updrafts and downdrafts exist simultaneously.

    Eventually, the storm’s power begins to wane as the downdrafts cut off the updrafts that feed the storm. Sometimes this occurs in a massive downdraft where cool air sinks straight down and, upon encountering the ground, spreads radially outward. In dry regions, this outward burst of ground-level winds can pick up dirt, dust, and sand, forming a wall-like haboob (below) that advances past the remains of the storm. Watch the entire video to see some examples in their full glory! (Video and image credit: M. Olbinski, source; via Rex W.)

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  • Lagoon Flows

    Lagoon Flows

    The meeting of land and sea often creates a rich and colorful environment. This satellite image shows Mexico’s Laguna de Términos, a coastal lagoon off the Gulf of Mexico. A skinny barrier island forms the lagoon’s two connections to the ocean; the eastern side is the usual inlet (right), while the western side forms an outlet. Rivers feed freshwater into the lagoon from the south and southwest. These introduce sediments that cause some of the lighter swirls in the image. Winds and tides also contribute to this turbidity. The sheltered nature of the lagoon allows fresh and salt water to mix gradually, providing harbor for many forms of life. Oyster beds thrive in the river mouths; seagrasses prefer the calmer, saltier waters, and mangrove trees line the shore, slowly desalinating water for themselves as their roots shelter young fish and shrimp. (Image credit: NASA Earth Observatory)

  • Oceans of Clouds

    Oceans of Clouds

    One of the most amazing things about fluid dynamics, in my opinion, is that the same rules apply across an incredible array of situations. The equations of motion are the same whether your fluid is water, air, or honey. Your flier can be a Cessna airplane or a fruit fly; again, the equations are the same. This is part of the reason that patterns in flows are repeated whether in the laboratory or out in nature – and it’s the reason why a timelapse of fog clouds can look just like ocean waves. Ultimately, the physics is the same; clouds just move slower than ocean waves! (Image credit: L. Leber, source; via James H.)

  • Symmetric Wakes

    Symmetric Wakes

    Nature is full of remarkable patterns and moments of symmetry. This image shows the wake behind two rotating cylinders. Half of the cylinders are visible at the far left. The flow moves left to right. The cylinders are rotating at the same rate but in opposite directions, clockwise for the cylinder on top and counter-clockwise for the bottom one. At this speed relative to the freestream, there is a beautiful symmetry to the vortices in the wake, but the researchers found that even a slight deviation from this condition quickly destroyed the pattern. The flow is visualized here by introducing tiny hydrogen bubbles via electrolysis. The bubbles are small enough that their buoyancy has no appreciable effect. (Image credit: S. Kumar and B. Gonzalez)

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    “Macrocosm”

    In “Macrocosm” artist Susi Sie explores a liquid world of black and white. The two colors diffuse and mix to a soundtrack of “space sounds” recorded by NASA. (Most of these are probably ionic sound rather than sound as we’re used to, but even that is somewhat fluid dynamical.) The result is beautiful, surreal, and more than a little creepy. Happy Halloween! (Video and image credit: S. Sie)

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  • Rheoscopic Flow Vis

    Rheoscopic Flow Vis

    One of the great challenges in visualizing fluid flows is the freedom of movement. A fluid particle – meaning some tiny little bit of fluid we want to follow – is generally free to move in any direction and even change its shape (but not mass). This makes tracking all of those changes difficult, and it’s part of why there are so many different techniques for flow visualization. The technique an experimenter uses depends on the information they hope to get.

    Often a researcher may want to know about fluid velocity in two or more directions, which can require multiple camera angles and more than one laser sheet illuminating the flow. An alternative to such a set-up is shown above. The injected fluid – known as a rheoscopic fluid – contains microscopic reflective particles, in this case mica, that are asymmetric in shape. Imagine a tiny rod, for example. By illuminating the rod from different directions with different colors of light, you can determine the particle’s orientation based on the color it reflects. Since the orientation of the particle depends on the surrounding flow, you can infer how the flow moves. (Image credit and submission: J. C. Straccia; research link: V. Bezuglyy et al.)

  • Sunset Vortices

    Sunset Vortices

    Often our atmosphere’s transparency masks the beautiful flows around us. This spectacular image shows a flight landing in Munich just after sunrise. Low-hanging clouds get sliced by the airplane’s passage and curl into its wake. The swirls are a result of the plane’s wingtip vortices, which wrap from the high-pressure underside of the wing toward the low-pressure upperside. The vortices stretch behind in the plane’s wake, creating turbulence that can be dangerous to following planes. In fact, these vortices are a major determining factor in the frequency of take-off and landing on a given runway. The larger a plane, the larger its wingtip vortices and the more time it takes for the turbulence of its passage to dissipate to a safe level for the next aircraft. (Image credit: T. Harsch; submitted by Larry S.)

  • Tightrope Walkair

    Tightrope Walkair

    A bubble rising through water can get caught on an aerophilic (air-attracting) fiber. The bubble will then adhere to the fiber and be guided to the surface by it. In the poster above, the image is a composite photo of such a bubble every 40 milliseconds. Once captured by the fiber, the bubble first accelerates and then reaches a terminal velocity, indicated by the equal spacing of the bubble photos toward the right end of the picture. The terminal velocity strikes a balance between buoyancy, which pulls the bubble upward, and skin friction between the bubble and the water, which acts like drag on the bubble. At the terminal velocity, these forces are equal; neither is able to speed up or slow down the bubble. (Image credit: H. de Maleprade et al.)

  • Wrinkling Drops

    Wrinkling Drops

    When a viscous drop falls into a pool of a less viscous liquid, the drop can deform into some beautiful and complex shapes. Typically, shear forces between the drop and its surroundings cause a vortex ring to roll up and advect downward, thereby stretching the remainder of the drop into thin sheets that can buckle and wrinkle. Here the drop is about 150 times more viscous than the pool and impacts at 1.45 m/s, making a rather energetic entry. The vortex ring (not visible) has stretched the drop’s remains downward while a buoyant bubble caught by the impact pulls some of the drop back toward the surface. As a result, the thin sheets of the drop’s fluid are buckling and folding back on themselves like an elaborate and delicate glass sculpture. This entire paper is full of gorgeous images and videos. Be sure to check them out! (Image and research credit: E. Q. Li et al.; see supplemental info zip for videos)

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    Songs in Soap

    There are many beautiful ways to visualize sound and music – Chris Stanford’s fantastic “Cymatics” music video comes to mind – but this is one I haven’t seen. This visualization uses a soap film on the end of an open tube with music playing from the other end. You can see the set-up here. The result is a fascinating interplay of acoustics, fluid dynamics, and optics. As sound travels through the tube, certain frequencies resonant, vibrating the soap film with a standing wave pattern (3:20). At the same time, interference between light waves reflecting off the front and back of the soap film create vibrant colors that show the film’s thickness and flow.

    When the frequency and amplitude are just right, the sound excites counter-rotating vortex pairs in the film (0:05), mixing areas of different thicknesses. With just a single note, the vortex pairs appear and disappear, but with the music, their disappearance comes from the changing tones. Watching the patterns shift as the film drains and the black areas grow is pretty fascinating, but one of the coolest behaviors is how the acoustic interactions are actually able to replenish the draining film (2:15). Because the tube was dipped in soap solution, some fluid is still inside the tube, lining the walls. With the right acoustic forcing, that fresh fluid actually gets driven into the soap film, thickening it.

    There are several more videos with different songs here – “Carmen Bizet” is particularly neat – as well as a short article summarizing the relevant physics for those who are interested. (Video and research credit: C. Gaulon et al.; more videos here)