FYFD

Tag: Coriolis effect

  • Devising Greener Chemistry

    Devising Greener Chemistry

    Not all microfluidic devices use tiny channels to pump and mix fluids. Some, like the Vortex Fluidic Device (VFD), conduct their microfluidic mixing in thin films of fluid. The VFD is essentially a tube spinning at several thousand RPM that can be tilted to various angles. Coriolis forces, shear, and Faraday instabilities in the thin fluid film create a complex microfluidic flow field that’s excellent for mixing, crystallization, and processing of injected chemicals. One rather notorious application of this device was unboiling an egg, a feat for which the researchers won an Ig Nobel Prize. But other, more practical applications abound, including a waste-free method for coating particles. (Image and research credit: T. Alharbi et al.; video credit: Flinders University; via Cosmos; submitted by Marc A.)

  • Understanding Jupiter

    Understanding Jupiter

    The swirling clouds of Jupiter hide a complicated and mysterious interior. For decades, scientists have worked to puzzle out the inner dynamics of Jupiter’s atmosphere and what could be going on inside it to generate the flows we see visibly. Near Jupiter’s equator, we see strong jets that flow either east or west, depending on their latitude; this creates the stunning cloud bands we’re used to seeing on the planet. Toward the poles, though, things look more like what we see above – swirling but unbanded.

    Through theory, experiments, and simulations, scientists have tried to work out exactly what ingredients are necessary to make Jupiter look this way, but it’s pretty tough to recreate the conditions simply because Jupiter is so extreme. You need a lot of rotation, a lot of turbulence, and a way to stretch that turbulence if you want to imitate Jupiter. There’s been progress recently, though, and it suggests that the jets we see on Jupiter are far more than skin-deep. Instead, they likely stretch deep into the Jovian atmosphere at the equator and ride somewhat shallower toward the poles. (Image credit: NASA JPL; research credit: S. Cabanes et al.)

  • Featured Video Play Icon

    Bees, Squid, and Oil Plumes

    It’s time for another JFM/FYFD collab video! April’s video brings us a taste of spring with research on how bees carry pollen, squid-inspired robotics, and understanding the physics of underwater plumes like the one that occurred in the Deepwater Horizons spill eight years ago. Check it all out in the video below. (Image and video credit: T. Crawford and N. Sharp)

  • In the Eye of a Hurricane

    In the Eye of a Hurricane

    Although eyes are common at the center of large-scale cyclones, scientists are only now beginning to understand how they form. Since real-world cyclogenesis is complicated by many competing effects, researchers look at simplified model systems first. A typical one uses a shallow, rotating cylindrical domain in which heat rises from below. The rotation provides a Coriolis force, which shapes the flow. In particular, it causes a boundary layer along the lower surface of the domain, creating a thin region where the flow moves radially inward. (Its opposite forms at the upper surface of the domain, sending flow radiating outward.) Like an ice skater spinning, the flow’s vorticity intensifies as it approaches the central axis of rotation. When the conditions are right, this intensely swirling boundary layer flow lifts up into the main flow, forming an eyewall. The eye itself, it turns out, is merely a reaction to the eyewall’s formation. (Image credit: S. Cristoforetti/ESA; research credit: L. Oruba et al.)

  • Coastal Upwelling

    Coastal Upwelling

    Cool temperatures and abundant nutrients make the waters off the western coast of North America especially biologically productive. This image is a composite of satellite data highlighting large phytoplankton blooms in the California Current. This current runs southward along the coastline, and, like other eastern boundary currents, it experiences strong upwelling, or rising of colder, nutrient-rich waters from lower depths. The upwelling is driven in part by Earth’s rotation. As the earth spins, Coriolis effects push the California Current out from the coast, allowing deeper waters to rise and fill the void. The cooler water provided by the upwelling is a major factor in the moderated climate along the West Coast. (Image credit: NASA/N.Kuring; via NASA Earth Observatory)

  • Coriolis

    Coriolis

    There’s an infamous supposition about drains swirling one way in the Northern Hemisphere and the other way in the Southern Hemisphere. Destin from Smarter Every Day and Derek from Veritasium have put the claim to the test with experiments on either side of the globe. First, go here and watch their synchronized videos side-by-side. (To synchronize, start the left video and pause it at the sync point. Then start the second video and unpause the first video when the second video hits the sync point.) I’ll wait here.

    …

    That was awesome, right?! The demonstration doesn’t work with toilets because they’re driven by the placement of jets around the circumference. And your bathtub doesn’t usually work either because any residual vorticity in the tub gets magnified by conservation of angular momentum as it drains. It’s like a spinning ice skater pulling their arms in; the rotation speeds up. So, to get around that problem, Destin and Derek let their pools sit for a day to damp out any motion before draining. At that point, the Coriolis effect is strong enough to cause the pools to rotate in opposite directions when drained. You may wonder why the effect is so slight for the pools when it’s pretty stark with hurricanes and cyclones. The answer is a matter of scale. The pools are perhaps 2 meters wide, which means that the difference in latitude across the the pool is very slight and therefore, the differential speed imparted by the Earth’s rotation is also very small. Because hurricanes and cyclones are much larger, they experience stronger influence from the Coriolis effect. (Image credits: Smarter Every Day/Veritasium; via It’s Okay To Be Smart)

  • Featured Video Play Icon

    Turning Into 2D

    UCLA Spinlab has another great video demonstrating the effects of rotation on a fluid. In a non-rotating fluid, flow over an obstacle is typically three-dimensional, with flow moving over as well as around the object. But in a steadily rotating fluid, as shown in the latter half of the video, the flow only moves around the obstacle, not over it. This non-intuitive behavior is part of the Taylor-Proudman theorem, which shows that flow around an obstacle in a rapidly rotating fluid will be two-dimensional and confined to planes perpendicular to the axis of rotation. (For the mathematically-inclined, Wikipedia does have a short derivation.) This 2D flow creates what are called Taylor columns over the obstacle. The Taylor column is like an imaginary extension of the original obstacle, turning the puck into a tall cylinder, and it’s real enough to flow, which diverts around it as though the column were there. (Video credit: UCLA Spinlab)

  • Featured Video Play Icon

    Rotational Effects

    Rotation can cause non-intuitive effects in fluid dynamical systems. UCLA Spinlab’s newest video tackles the problem using four demonstrations. The first two deal with droplets released in air, first in a non-rotating environment and then in a rotating one. As one would expect, in a non-rotating environment, droplets fall through the tank in a straight line. When rotating, though, the droplets follow a deflected, straight-line path due to centrifugal effects. This is the same as the way passengers in a car feel like they’re being thrown to the outside of a turn on a curvy road. When the experiment is repeated with a tank of water instead of air, the results are different. The densities of the creamer and water are much closer to one another, so the droplet falls much slower than before. The tank now rotates faster than time it takes the drop to fall. This smaller timescale means that the droplet experiences more acceleration from Coriolis forces than centrifugal forces in the rotating tank of water. Thus, instead of being thrown outward, the drop now forms a column aligned with the axis of rotation. (Video credit: UCLA Spinlab; submitted by Jon B.)

  • Featured Video Play Icon

    Rotating or Not-Rotating?

    Rotating a fluid often produces different dynamical behavior than for a non-rotating fluid.  Here this concept is demonstrated by dropping creamer into a tank of water.  Both experiments produce a turbulent plume, but the way the plume spreads and diffuses is much different in the case of the rotating tank, thanks to the Coriolis effect. (Video credit: SPINLab UCLA)