It’s only fitting to take a moment to look back at 2014 as we step into the New Year. It was a big year in many respects - we hit 1000 posts and broke 200,000 followers; I started producing FYFD videos on our YouTube channel; and, on a personal note, I finished up my PhD. But since we’re all about the science around here, I will give you, without further ado, the top 10 FYFD posts of 2014:

1. Bioluminescent crustaceans use light for defense
2. What happens when you step on lava
3. Flapping flight deconstructed
4. Wingtip vortices demonstrated
5. Saturn’s auroras
6. Raindrops’ impact on sand
7. Water spheres in microgravity
8. The surreal undulatus asperatus cloud
9. Inside a plunging breaker
10. A simply DIY Marangoni effect demo

I can’t help but notice that 9 out of the 10 posts feature animated GIFs. Oh, Tumblr, you rascals. Happy New Year! (Image credits: BBC; A. Rivest; E. Lutz; Nat. Geo/BBC2; ESA/Hubble; R. Zhao et al.; D. Petit; A. Schueth; B. Kueny and J. Florence; Flow Visualization at UC Boulder)


Turbidity currents are a gravity-driven, sediment-laden flow, like a landslide or avalanche that occurs underwater. They are extremely turbulent flows with a well-defined leading edge, called a head. Turbidity currents are often triggered by earthquakes, which shake loose sediments previously deposited in underwater mountains and canyons. Once suspended, these sediments make the fluid denser than surrounding water, causing the turbidity current to flow downhill until its energy is expended and its sediment settles to form a turbidite deposit. By sampling cores from the seafloor, scientists studying turbidites can determine when and where magnitude 8+ earthquakes have occurred over the past 12,000+ years!  (Video credit: A. Teijen et al.; submitted by Simon H.)

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A good soccer player can kick the ball from the corner of the field into the goal thanks to the Magnus effect. But if you’ve ever tried to play soccer with a smooth ball, you may have noticed that sometimes the ball bends the wrong way! This is the reverse Magnus effect and it’s caused when the boundary layers on either side of the ball switch from turbulent to laminar flow at different times. Dianna Cowern explains (with a little help from yours truly) in the video above. Want to learn more about how roughness affects boundary layers? Check out our companion video on FYFD’s YouTube channel. (Video credit: D. Cowern/Physics Girl)


Pouring cream in coffee produces some of the most mesmerizing displays of fluid dynamics. The density difference between the two fluids sets up Rayleigh-Taylor instabilities that mushroom out and help create the turbulence that eventually mixes the drink. You can learn more about Rayleigh-Taylor instabilities in this FYFD video, and, if you need more awesome caffeine-filled examples of fluids, check out the coffee dynamics blog. (Video credit: S. Geraldine and L. Kang)


The icy plain of Sputnik Planum, located in Pluto’s heart-shaped Tombaugh Reggio, is criss-crossed with troughs that divide the plain into polygons.  The current interpretation of these features is that they are the result of thermal convection. As with Rayleigh-Benard convection cells on Earth, the interior of the polygons is formed by the upwelling of warmer, buoyant material, and the troughs between cells mark locations where cooled material convects back into the mantle. On Pluto, these cells consist of nitrogen ice (and occasional water ice like the dirty black chunk seen in the upper right photo) that slowly rises and sinks from the planet’s surface, constantly refreshing the surface features. This would explain why Sputnik Planum is missing evidence of typical older features like impact craters. (Image credits: NASA/JHU APL/SwRI)

Join FYFD all this week for a look at fluid dynamics and planetary science on Pluto! Check out the previous posts here.

Off on a vacation

Hey guys,

Tomorrow (October 14), I’m heading off on vacation for a couple weeks out of range of the Internet. I’ve queued up entries for while I’m gone and my friend Claire from Brilliant Botany (check it out!) has kindly agreed to watch over the Tumblr queue and make sure it posts like it’s supposed to. So you should hopefully experience no interruptions to regular posts. But I won’t be responding to asks, submissions, emails, etc. until after I return at the end of the month.

Have a lovely October, readers! I’m off in search of penguins and iguanas.



Originally posted: 22 July 2010 This video of the NASA Solar Dynamics Observatory’s launch is such a favorite of mine that it was part of the original inspiration for FYFD and was the very first video I posted. Watch closely as the Atlas V rocket climbs. At 1:51 you’ll see a rainbow-like cloud in upper right corner of the screen. This effect is created by sunlight shining through ice crystals of the cloud. A couple seconds later you see pressure waves from the rocket propagate outward and destroy the rainbow effect by re-aligning the ice crystals. Just after that comes the announcement that the vehicle has gone supersonic. The atmospheric conditions of the launch happened to be just right to make those pressure waves coming off the rocket visible just before they coalesced into a leading shockwave. (Video credit: B. Tomlinson)

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Here on FYFD, we like to show off the artistic side of fluid dynamics. But some researchers are actively studying how artists use fluid dynamics in their art. In this video, they examine one of Jackson Pollock’s painting techniques, in which filaments of paint were applied by flinging paint off a paintbrush. Getting the technique to work requires a fine balance of forces and effects. Firstly, the paint must be viscous enough to hold together in a filament when flung. Secondly, the centripetal acceleration of the rotation must be high to both form the catenary filament and throw it off the brush. And, finally, the Reynolds number needs to be high enough to add some waviness and instability to the filament so that it looks interesting once it hits the canvas. Also be sure to check out the group’s previous work exploring Siqueiros’s painting techniques. (Video credit: B. Palacios et al.)