The launch of the Solar Dynamics Observatory (SDO) last year provided a rarely seen glimpse of how shock waves affect the atmosphere during launch, but only recently have researchers explained the white column that seemed to follow SDO toward orbit. Simulations indicate that the shock waves from the rocket aligned the ice crystals in the atmosphere into an array of spinning tops. Individual crystals precess as a result of the rocket passing; the column is part of a larger oval that would have been visible had the ice crystals covered a larger range. See Wired for more. #
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How Ferrofluids Work
Here’s a ferrofluid video with a little more explanation about how ferrofluids work. Surfactants prevent the tiny magnetic particles suspended in the fluid from separating out when exposed to a magnetic field.
Geometrical Droplet Splashes
Sadly, this video shows no droplet impacts on a heart-shaped post, but maybe you can imagine what it would look like after seeing other geometrical shapes. Happy Valentine’s Day, guys!
Volcanic Turbulence
One of the characteristics of turbulence is its large range of lengthscales. Consider the ash plume from this Japanese volcano. Some of the eddy structures are tens, if not hundreds, of meters in size, yet there is also coherence down to the scale of centimeters. In turbulence, energy cascades from these very large scales to scales small enough that viscosity can dissipate it. This is one of the great challenges in directly calculating or even simply modeling turbulence because no lengthscale can be ignore without affecting the accuracy of the results. #
Dr. Seussian Mystery Fluid Could Have Saved Top Kill
Dr. Seussian Mystery Fluid Could Have Saved Top Kill
Wired article about using non-Newtonian fluids to plug leaking oil wells as we featured previously.
Plugging an Oil Leak
Recent research indicates that adding cornstarch to drilling mud increases the likelihood that a “top-kill” procedure will plug a leaking oil well. Adding cornstarch to water (or mud) turns it into a non-Newtonian fluid with viscoelastic properties that prevent the instabilities that lead to turbulent breakup. On the left, an underwater photo of the Deepwater Horizons leak; in the center, colored water breaks into turbulence when descending into oil; on the right, water with cornstarch maintains its coherence when pumped downward into the oil. # (PDF of research paper)
Saturnian Storm
Back in mid-December, amateur astronomers discovered an enormous new storm on Saturn. The Cassini spacecraft captured this image early in the storm’s history (it now stretches farther around the planet). The fluid dynamics of Saturn’s atmosphere are incredibly complex and well beyond our current understanding, but we can certainly appreciate the majesty of a swirling, turbulent storm half the size of our entire planet. (via APOD, Martian Chronicles)
Superfluid Helium Leaks from its Container
Below a temperature of 2.17 Kelvin, helium becomes a superfluid, a state of matter boasting several unique properties including zero viscosity (resistance to flow). In this video, scientists demonstrate that property. When they pull the glass “bucket” of helium out at 2:50, the helium starts to leak out. The glass is solid but it contains numerous tiny spaces between its atoms. In its normal state, the viscosity of helium prevents it from escaping through those holes. But as a superfluid, its resistance to flowing goes to zero and it leaks right through the solid glass.
Flying Paint
High speed footage of flying paint demonstrates a world of viscosity and surface tension, as well as another great example of fluid dynamics as art. (via Gizmodo)
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Ferrofluid Labyrinths
Here’s a different take on ferrofluids. Instead of spikes, we get 2D patterns reminiscent of these ones. Most likely the ferrofluid is trapped under glass as part of a Hele-Shaw cell. The results remind me some of chaotic Rayleigh-Benard convection cells, actually.