FYFD

Search results for: “art”

  • The Bathtub Vortex

    The Bathtub Vortex

    If you’ve ever watched a swirling vortex disappear down the drain of your bathtub and wondered what was happening, you’ll appreciate these images. This dye visualization shows a one-celled bathtub vortex, created by rotating a cylindrical tank of water until all points have equal vorticity before opening a drain in the bottom of the tank. A recirculating pump feeds water back in to keep the total fluid mass constant. Once a steady vortex is established, green dye is released from the top plate of the tank and yellow dye from the bottom. The green dye quickly marks the core of the vortex. Ekman layers–similar to the boundary layers of non-rotating flows–form along the top and bottom surfaces, and the yellow dye is drawn upward in a region of upwelling driven by Ekman pumping. (Photo credit: Y. Chen et al.)

    Just a reminder for those at Texas A&M University: I will be giving a talk today Wednesday, October 2nd entitled “The Beauty of the Flow” as part of the Applied Mathematics Undergraduate Seminar series at 17:45 in BLOC 164.

  • Featured Video Play Icon

    Maze-Solving Droplets

    The Leidenfrost effect occurs when liquids come in contact with a substrate much, much hotter than their boiling temperature. Rather than immediately boiling away, a thin layer of the liquid vaporizes and insulates the bulk of the liquid from the heat. This essentially turns droplets into tiny hovercrafts that skate over the surface. If you use a rough surface with rachets, the Leidenfrost drops will self-propel toward the steepest part of the rachet. The vapor underneath the drop is constantly trying to flow away, and the rachets in the surface prevent the vapor from escaping in the steeper direction. The vapor instead flows out the shallower side and–thanks to Newton’s third law–creates thrust that pushes the droplet the opposite direction. Here students from the University of Bath have used these effects to build a maze through which the droplets fly. (Video credit: C. Cheng et al.; via Flow Visualization FB page and several submissions)

    For readers at Texas A&M University, I will be giving a talk Wednesday, October 2nd entitled “The Beauty of the Flow” as part of the Applied Mathematics Undergraduate Seminar series at 17:45 in BLOC 164.

  • Oil Flow Viz

    Oil Flow Viz

    Fluorescent oil sprayed onto a model in the NASA Langley 14 by 22-Foot Subsonic Wind Tunnel glows under ultraviolet light. Airflow over the model pulls the initially even coat of oil into patterns dependent on the air’s path. The air accelerates around the curved leading edge of the model, curling up into a strong lifting vortex similar to that seen on a delta wing. At the joint where the wings separate from the body those lifting vortices appear to form strong recirculation zones, as evidenced by the spiral patterns in the oil. Dark patches, like those downstream of the engines could be caused by an uneven application of oil or by areas of turbulent flow, which has larger shear stress at the wall than laminar flow and thus applies more force to move the oil away. Be sure to check out NASA’s page for high-resolution versions of the photo. (Photo credit: NASA Langley/Preston Martin; via PopSci)

  • Beach Cusps

    Beach Cusps

    Beach cusps are arc-like patterns of sediment that appear on shorelines around the world. Cusps consist of horns, made up of coarse materials, connected by a curved embayment that contains finer particles. They are regular and periodic in their spacing and usually only a few meters across. A couple of theories exist as to how cusps form, but once they do, they are self-sustaining. When an incoming wave hits a horn, the water splits and diverts. The impact of the wave on the horn slows the water, causing it to deposit heavy, coarse particles on the horns while finer sediment gets carried up to the embayment before the wave flows back outward. (Photo credit: L. Tella; inspired by E. Wiebe)

  • Reader Question: Oceans Meeting?

    Reader Question: Oceans Meeting?

    Reader favoringfire asks:

    Hi! Maybe you can help me: I’ve seen a pic revolving around Tumblr from the Danish city of Skagen showing the Baltic and North sea meeting. Where they meet the ocean is two very distinct hues of blue–what captions say are “two opposing tides with different densities.” Tides? Currents w/different temps often are often diff color from one another. But can “tides” be of different “densities???”

    After some searching, I think the photo above is probably the one you’ve seen represented as where the Baltic and North Seas meet. It turns out, however, that it’s not. It’s a photo from an Alaskan cruise taken by Kent Smith. Fluid dynamically, though, it’s still very interesting! What we see here is a sharp gradient between regions with very different densities. One side contains lots of freshwater from rivers fed by melting glaciers, which creates a very different density from the general seawater.

    It’s not true, however, that the two won’t mix. This border is not a static phenomenon but one that is ever-changing due to currents and the diffusion of one fluid into another. In a sense, this photo is very much the sea-level version of photos like these which show the massive scale of sediment transport and nutrient mixing that occur in our oceans.

    (Photo credit: K. Smith)

  • Fluids Round-up – 21 September 2013

    Fluids Round-up – 21 September 2013

    First off, I’d like to give a special shout-out to FYFD’s friends at Pointwise, who were kind enough to invite me for a visit this week. For any readers looking for CFD grid-generation software, check them out; they are a fantastic bunch and very good at what they do.

    My thanks again to everyone who donated this week to help get me to the APS conference. The campaign is still open if anyone wants to get in on the FYFD wallpapers and stickers on offer to donors. As a reminder, any funds beyond conference costs will go toward improving FYFD, including getting equipment to make FYFD videos. On to the fluids round-up!

    (Photo credit: L. Gilman)

  • Ig Nobel Fluids: Shower Curtain Science

    Ig Nobel Fluids: Shower Curtain Science

    Nearly everyone has faced the frustration of a shower curtain billowing inwards to stick to one’s leg. Various explanations have been offered to explain the effect, but David Schmidt won the 2001 Ig Nobel Prize in Physics for a numerical simulation suggesting that the spray of droplets from the shower head drives a horizontal vortex whose axis of rotation is perpendicular to the shower curtain. Since vortices have a low-pressure region in their core, this weak shower vortex has the power to suck a light curtain inward, much to the chagrin of the shower’s occupant. Of course, a heavier or weighted shower curtain will help avoid the effect. This post is part of a series on fluids-related Ig Nobel Prizes. (Photo credit: W. Taylor; research credit: D. Schmidt)

  • Ig Nobel Fluids: Cookie Dunking

    Ig Nobel Fluids: Cookie Dunking

    Back in 1999 Len Fisher earned an Ig Nobel Prize in Physics for explaining the physics of dunking a biscuit or cookie in a liquid. The cookie is porous, with many tiny, interconnecting channels run throughout it. When dipped in a liquid, capillary action pulls the fluid up into these channels against the force of gravity. As most people discover, this wetting can soften the cookie to the point of collapse. The optimal manner of dunking then is to hold the cookie at a shallow angle; this allows the lower surface to soak in milk (or the hot beverage of your choice) while keeping the upper surface dry and structurally sound. Fisher further argued that Washburn’s equation, which describes the time necessary for capillary action to draw a liquid up a given length of a cylindrical pore gives a good estimate of the length of time for a cookie dunking. This proved so popular he even wrote a book about it. This is a part of a series on fluids-related Ig Nobel Prizes. (Photo credit: C. Lindberg; research credit: L. Fisher)

  • Featured Video Play Icon

    Ig Nobel Fluids: Running on Water

    While insects are small enough to use surface tension to stay atop water, larger species like the basilisk lizard run on water by slapping their feet against the surface hard enough to generate the force to stay above the surface. A. Minetti and colleagues won this year’s Ig Nobel Prize in Physics for demonstrating that humans, too, can achieve this feat – when outfitted with stiff, large area fins and exposed to gravity less than 22% of Earth’s. The researchers adapted a model for the running lizard to human scales and then tested the model using subjects suspended by harness and running in place atop a wading pool while subjected to various lighter-than-earth simulated gravities. Both the model and experiment agreed that human muscles were unable to produce sufficient force to stay above the water at higher than 0.22g. Interestingly, the authors also observed that the water-running gait for both lizards and humans has more in common with the pedaling motion of cycling than a human’s bouncing gait for terrestrial running. (Video credit: A. Minetti et al.)

  • Ferrofluid Thrusters

    Ferrofluid Thrusters

    Ferrofluids–magnetically-sensitive fluids made up of a carrier liquid and ferrous nanoparticles–may soon have a new application as a miniature thruster on nanosatellites. Microspray thrusters use tiny hollow needles to electrically spray jets of liquid that propel a satellite. But manufacturing the fragile microscopic needles used to disperse the propellant is expensive. Instead researchers are now using ferrofluids to create both the needle-like structures and to serve as the propellant. A ring of ferrofluid is placed on the thruster surface and a magnetic field applied to create the ferrofluid’s distinctive spikes. Then, when an electric force is applied, tiny jets of ferrofluid spray out from each tip, creating thrust. Unlike the conventional needles, the ferrofluid spikes are robust and can reform after being disturbed. (Photo credit: L. B. King et al.; submitted by jshoer)

More posts