This NASA Langley Research Center test shows real-time flow visualization of the wingtip vortices off a C-5A Galaxy aircraft.
Tag: fluid dynamics
Drinking Coffee in Space
Operating in microgravity disrupts a lot of everyday routines. However, astronauts have learned to take advantage of surface tension to enable them to drink their daily coffee from a cup still.
Phytoplankton in Bloom
Phytoplankton blooms, aside from giving us gorgeous eddies of blue and green, can reveal how ocean currents are mixing. Blooms typically occur where nutrients are being washed together. #
The Sound of Helium
Gases of different density are good for more than just physics demonstrations. They also affect the transmission of sound waves, thereby altering our perception of pitch. As fun as sulfur hexafluoride is, though, don’t go playing with it at home; it’s an extremely potent greenhouse gas.
The Bouncing Jet
Under some circumstances, a thin stream of a Newtonian fluid impacting a deep pool of the same fluid can produce a bouncing jet. The effect is observed in common liquids like canola oil and can be replicated at home. Be sure to check the research page for a video of the effect. #
Running on a Pool of Oobleck
What happens when you fill a pool with a non-Newtonian fluid? Well, for one, you can hold races across the surface! In this video, the pool is filled with a mixture of cornstarch and water, a shear-thickening fluid known as oobleck.
Dripping into Droplets
The Plateau-Rayleigh instability is one that just about everyone has witnessed. It describes how a liquid jet breaks up into droplets. Notice the waviness in the jet before breakdown. The tiniest curvature in the jet causes an imbalance in the liquid’s pressure due to surface tension. Because the system is unstable, any small changes will become larger, ultimately resulting in the jet breaking into droplets.
How to Grow Straight Icicles
New research suggests that icicles grow straighter when exposed to moving air while exposure to still air can cause icicles to sprout at their tips. To grow icicles, the researchers built a refrigerated box that dripped water from the top while the growing icicle rotated. Understanding ice growth is important for flight aerodynamics and icing on airplane wings. For videos and more on icicle growth, see the article at Wired Science. #
Happy Anniversary, Enterprise!
Wind tunnels are great, but there’s nothing like a flight test to learn about the aerodynamics of a new vehicle. Today in 1977, the space shuttle prototype Enterprise flew on its own for the first time. Enterprise was built purely to test the shuttle’s aerodynamic behavior during gliding and landing. Check out this video of one of Enterprise’s gliding and landing tests.
Un-mixing a Flow
Laminar flow (as opposed to turbulence) has the interesting property of reversibility. In this video, physicists demonstrate how flow between concentric cylinders can be reversed such that the initial fluid state is obtained (to within the limits of molecular diffusion, of course!)
For more examples, see the first half of this video.
