FYFD

Tag: flow visualization

  • Recreating Infinity

    Recreating Infinity

    In the ocean, tiny organisms can migrate hundreds of meters through the water column. Recreating and tracking those journeys in a lab is quite a challenge, but it’s one the researchers behind the Gravity Machine have conquered. This apparatus uses a wheel to essentially give micro-organisms an infinite water column to traverse while keeping them fixed in the lab microscope’s field of view.

    With the device, researchers can watch organisms switch naturally between rising, sinking, and feeding behaviors as they would in the wild. The group is working to make it so that anyone with a microscope can recreate their set-up for observations. (Image, video, and research credit: D. Krishnamurthy et al.; see also Gravity Machine; submitted by Kam-Yung Soh)

  • Green Swirls and Dark Streaks

    Green Swirls and Dark Streaks

    Green phytoplankton blooms swirl through the currents of the Baltic Sea in this satellite image. Individual phytoplankton are microscopic, which makes them excellent tracer particles in the flow; together, they make the ocean’s motion visible. Look closely and you’ll see dark streaks across the images showing where ships’ wakes are disrupting the bloom. (Image credit: J. Stevens/USGS; via NASA Earth Observatory)

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    “Colors”

    Paint, soap, bleach, oil, and oat milk combine to create the gorgeous colorscapes of Thomas Blanchard’s short film “Colors”. Watch as droplets burst and waves of color flow past. It’s a lovely break from whatever you’re dealing with at the moment, and at less than 3 minutes long, you can spare the time! (Image and video credit: T. Blanchard)

  • A Colorful Portrait of Flow

    A Colorful Portrait of Flow

    This gorgeous, natural-color image shows Lake Balkhash in southeastern Kazakhstan. In early March, the ice on the lake was beginning to break up, revealing glimpses of swirling sediment below the water’s surface. In contrast, the smaller lakes and ponds of the surrounding area remained frozen amidst the wintery browns of the nearby desert and wetlands. (Image credit: J. Stevens/USGS; via NASA Earth Observatory)

  • Vortex Rings on V-Shaped Walls

    Vortex Rings on V-Shaped Walls

    Vortex ring impacts are eternally fascinating. Here, researchers explore what happens when a vortex ring encounters a V-shaped wall. Because the outer portions of the vortex ring hit the wall sooner than the inner ones, distortions begin there first.

    The vortex’s approach creates a pressure gradient that causes flow near the wall to separate, generating that first little hook in each arm of the vortex. Next, secondary vortices develop on either side and quickly get pulled into the original vortex. The whole process repeats a second time to generate tertiary vortices that continue the inward spiral. The impact appears even more complicated when viewed from the side of the valley (Image 2). Check out Image 3 for a point-by-point breakdown of the impact process. (Image and research credit: T. New et al.)

  • Contrails From 4 Engines

    Contrails From 4 Engines

    The wingtip vortices of aircraft provide a veritable cornucopia of gorgeous imagery. There’s something inherently fascinating about these vortices that stretch behind moving aircraft. But four-engine aircraft add an extra twist to the imagery, as seen here.

    With four engines, these aircraft produce four separate contrails, each of which acts like a streakline for the flow behind the wing. So what we see in these images is not the wingtip vortices themselves, but what their effect is on flow moving across different parts of the wing.

    Nearby vortices influence one another, and one of the earliest models of aircraft physics takes advantage of this by modeling the wing itself as a series of vortices. Odd as it sounds, such models are quite good for capturing the basic flow physics behind a finite wing.

    Using one of these models, Joseph Straccia explored the physics of a 4-engine aircraft’s wake (Image 4), predicting that the outboard engine contrails should initially move outward before getting rolled up and inward by the wingtip vortices. That’s exactly what we see in these images, particularly Image 1. The inboard contrails undergo less deflection, as expected since they are further from the wingtips. (Image credits: aircraft and contrails – JPC Van Heijst, J. Willems, and E. Karakas; modeling and submission – J. Straccia)

  • As the Fog Rolls In

    As the Fog Rolls In

    Although we talk about fog rolling in, it’s rare for us to have a perspective where we can truly appreciate that flow. But this photograph from Tanmay Sapkal provides just that for the low summer fogs sweeping over Marin, CA. When hot summer temperatures make inland air rise, cold, moist air from the ocean sweeps in to replace it. Once the moisture condenses, it forms thick, low clouds of fog that surge past the Golden Gate Bridge and into San Francisco Bay. (Image credit: T. Sapkal; via NatGeo)

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    Dendritic

    “What happens when two scientists, a composer, a cellist, and a planetarium animator make art?” The answer is “Dendritic,” a musical composition built directly on the tree-like branching patterns found when a less viscous fluid is injected into a more viscous one sandwiched between two plates.

    Normally this viscous fingering instability results in dense, branching fingers, but when there’s directional dependence in the fluid, the pattern transitions instead to one that’s dendritic. In this case, that directionality comes from liquid crystals, whose are rod-like shape makes it easier for liquid to flow in the direction aligned with the rods.

    For more on the science, math, and music behind the piece, check out this description from the scientists and composer. (Video, image, and submission credit: I. Bischofberger et al.)

  • Bright Volcanic Clouds

    Bright Volcanic Clouds

    Every day human activity pumps aerosol particles into the atmosphere, potentially altering our weather patterns. But tracking the effects of those emissions is difficult with so many variables changing at once. It’s easier to see how such particles affect weather patterns somewhere like the Sandwich Islands, where we can observe the effects of a single, known source like a volcano.

    That’s what we see in this false-color satellite image. Mount Michael has a permanent lava lake in its central crater, and so often releases sulfur dioxide and other gases. As those gases rise and mix with the passing atmosphere, they can create bright, persistent cloud trails like the one seen here. The brightening comes from the additional small cloud droplets that form around the extra particles emitted from the volcano.

    As a bonus, this image includes some extra fluid dynamical goodness. Check out the wave clouds and von Karman vortices in the wake of the neighboring islands! (Image credit: J. Stevens; via NASA Earth Observatory)

  • Bacterial Turbulence

    Bacterial Turbulence

    Conventional fluid dynamical wisdom posits that any flows at the microscale should be laminar. Tiny swimmers like microorganisms live in a world dominated by viscosity, therefore, there can be no turbulence. But experiments with bacterial colonies have shown that’s not entirely true. With enough micro-swimmers moving around, even these viscous, small-scale flows become turbulent.

    That’s what is shown in Image 2, where tracer particles show the complex motion of fluid around a bacterial swarm. By tracking both the bacteria motion and the fluid motion, researchers were able to describe the flow using statistical methods similar to those used for conventional turbulence. The characteristics of this bacterial turbulence are not identical to larger-scale turbulence, but they are certainly more turbulent than laminar. (Image credits: bacterium – A. Weiner, bacterial turbulence – J. Dunkel et al.; research credit: J. Dunkel et al.; submitted by Jeff M.)