FYFD

Month: September 2013

  • Thank You!

    Thank You!

    I have the best readers in the world. Seriously, everyone one of you is amazing. In less than 23 hours, you have blown past the goal I set. I will be going to the APS Division of Fluid Dynamics meeting thanks to you. THANK YOU!

    For those of you reading who will be at APS, I plan to do my utmost to be available to grab a coffee between sessions, hang out, discuss research, talk outreach, go out to dinner – whatever! For those of you who won’t be there, I want to share as much of the experience as possible with you through social media. Prepare to be inundated at the end of the November. Without all of you, I wouldn’t be at APS, and I’d like everyone who contributed to have a chance to enjoy the experience.

    Per IndieGoGo’s terms, the campaign will remain open until its October 11th deadline. Any contributions I receive above and beyond my APS costs, I plan to set aside for improvements to FYFD. The reader survey indicated lots of you would like me to make my own videos, and I aim to. Extra funds will first go toward equipment for that purpose.

    Thank you again to each and every one of you, whether you contributed your money or helped spread the word. I appreciate everything you’ve done for me and will continue striving to bring the best of fluid dynamics to FYFD every weekday. Thank you all!

  • 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)

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    Help FYFD Get to APS DFD 2013

    Readers, I need your help! Funding for my project got cancelled prematurely thanks to sequester-induced budget cuts and my research group no longer has the funds to send me to the American Physical Society’s Division of Fluid Dynamics meeting where I am scheduled to give two talks, one about FYFD and one about my research. APS’s DFD meeting is the big fluid dynamics conference of year, where thousands of researchers, professionals, and students come together to present their work. It’s always a major source of beautiful, interesting, and exciting photos and videos for FYFD. I’m asking you to help me raise the $2000 I need to attend. Watch the video, check out the perks available for donors over at IndieGoGo, and please help me spread the word by reblogging, retweeting, etc. Thank you!

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    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.)

  • Fluid Dynamics and the Nobel Prize

    Fluid Dynamics and the Nobel Prize

    Last night marked the 2013 Ig Nobel Prize Award Ceremony, in which researchers are honored for work that “makes people LAUGH and then THINK”. Historically, the field of fluid dynamics has been well-represented at the Ig Nobels with some 13 winners across the fields of Physics, Chemistry, Mathematics, and–yes–Fluid Dynamics since the awards were introduced in 1991. This is in stark contrast to the awards’ more famous cousins, the Nobel Prizes.

    Since the introduction of the Nobel Prize in 1901, only two of the Physics prizes have been fluids-related: the 1970 prize for discoveries in magnetohydrodynamics and the 1996 prize for the discovery of superfluidity in helium-3. Lord Rayleigh (a physicist whose name shows up here a lot) won a Nobel Prize in 1904, but not for his work in fluid dynamics. Another well-known Nobel laureate, Werner Heisenberg, actually began his career in fluid dynamics but quickly left it behind after his doctoral dissertation: “On the stability and turbulence of fluid flow.”

    This is not to suggest that no fluid dynamicist has done work worthy of a Nobel Prize. Ludwig Prandtl, for example, revolutionized fluid dynamics with the concept of the boundary layer (pdf) in 1904 but never received the Nobel Prize for it, perhaps because the committee shied from giving the award for an achievement in classical physics. General consensus among fluid dynamicists is that anyone who can prove a solution for turbulence using the Navier-Stokes equation will likely receive a Nobel Prize in addition to a Millennium Prize. In the meantime, we carry on investigating fluids not for the chance at glory, but for the joy and beauty of the subject. (Image credits: Improbable Research and Wikipedia)

  • Selective Suction

    Selective Suction

    A thin spout of water is drawn up through a layer of oil in the photo on the right. This simple version of the selective withdrawal experiment is illustrated in Figure A, in which a layer of viscous oil floats above a layer of water. A tube introduced in the oil sucks fluid upward. At low flow rates, only the oil will be drawn into the tube, but as the flow rate increases (or the tube’s height above the water decreases), a tiny thread of water will be pulled upward as well. The viscous outer fluid helps suppress instabilities that might break up the inner fluid, and their relative viscosities determine the thickness of the initial spout. In this example, the oil is 195 times more viscous than the water. (Photo credit: I. Cohen et al.)

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    Wind Tunnel Testing

    Wind tunnel testing is an important step in designing new aircraft. This video shows footage of visualization tests of the 21-ft wingspan Boeing X-48C model in NASA Langley’s Full-Scale Tunnel. The X-48C is a blended wing body design capable of higher lift-to-drag ratios than conventional aircraft, which should lead to a higher range and greater fuel economy. The video shows some smoke visualization that illustrates airflow around the airfoil-shaped craft. The long probe sticking forward from the starboard wing is used to measure air pressure, angle of attack, and sideslip angle of the model. Notice how smoke from the wand is pulled from below the leading edge of the wing up and over the top of the wing. This is because there is lower pressure over the top of the wing than the bottom, and, like an electrical charge seeking the path of least resistance, fluids flow preferentially toward lower pressures. (Video credit: NASA Langley)

  • 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)

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    Liquids Pinching Off

    There is a surprising variety of forms in the pinch-off of a liquid drop. This short video shows three examples, and you’ll probably find yourself replaying it a few times to catch the details of each. On the left, a drop of water pinches off in air. As the neck between the nozzle and the drop elongates, the drop end of the neck thins to a point around which the drop’s surface dimples. This is called overturning. When the drop snaps off, the neck disconnects and rebounds into a smaller satellite droplet. The middle video shows a drop of glycerol, which is about 1000 times more viscous than water. This droplet stretches to hang by a thin neck that remains nearly symmetric on the nozzle end and the drop end. There is no satellite drop when it breaks. The rightmost video shows a polymer-infused viscoelastic liquid pinching off. This liquid forms a very long, thin thread with a fat satellite drop still attached. When gravity eventually becomes too great a force for the stresses generated by the polymers in the liquid, the drops break off. (Video credit: M. Roche)

  • Spiraling Break-up

    Spiraling Break-up

    Instabilities in fluids are sometimes remarkable in their uniformity. Here we see a hollow spinning cup with a thin film of fluid flowing down the interior. The rim of fluid at the cup’s lip stretches into long, evenly spaced, spiraling threads. These filaments stretch until centrifugal forces overcome surface tension and viscous forces and break the liquid into a multitude of tiny droplets. This process is called atomization and is vital to everyday applications like internal combustion and inkjet printing. (Photo credit: R. P. Fraser et al.)