Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Tip Vortices
Like airplane wings, helicopter blades have tip vortices. In this photo, the air’s humidity was great enough that the acceleration caused by the passing of the blades caused a pressure drop great enough to condense the moisture, making the tip vortices visible to the naked eye. (See also Prandlt-Glauert singularity.) Photo credit: Gizmodo.
Effects of Viscosity
[original media no longer available] Today’s video demonstrates the effect of viscosity, which measures a fluid’s resistance to deformation. On the left is a column of highly viscous fluid; the fluids become less viscous as one moves right. When a jet of dye is released into the highly viscous fluid, the jet is very slow…
Zero-G Water Bubbles
Astronaut Don Pettit narrates some of his experiments with air and water droplets in microgravity in this video. The lack of body forces and buoyancy in microgravity means that surface tension effects frequently dominate. Pettit’s demonstrations also involve some fun basic physics with bubble behaviors inside of water droplets. See more of Pettit’s Saturday Morning…
Stirring with Electromagnetism
If a fluid is electrically conductive, then magnetohydrodynamics (often abbreviated as MHD) describe its behavior. Electric and magnetic fields can be used to stir such a fluid, as in the video above. By inducing a potential difference across the electrodes lining the walls and the disk-shaped electrodes far from the walls, complicated flow patterns can…
Water Balloon Photography
Photographer Edward Horsford uses high-speed photography to capture water balloons as they burst. On Earth, of course, gravity wins over surface tension, but the results are very different in microgravity. See the technical description for how Horsford gets his shots and look at more of his work on Flickr. (via NPR)
Wave Pool
This Japanese pool, lined with computer-controlled actuators, uses the principle of wave interference to create complex shapes at the center of the pool. While we may be more familiar with wave interference using light or sound, the principles remain the same for a wave in a fluid. (via Gizmodo and phredgreen)
Three Flows in One
These plumes of smoke demonstrate the three types of fluid flow: laminar, transitional, and turbulent. At the bottom of the photo, the plumes are smooth and orderly, as is typical for laminar flow. At the top, the smoke’s movement is chaotic and intermittent, full of turbulent eddies. Between these two stages, the flow is in…
Seeing Shock Waves with Schlieren
Schlieren photography is actually a pretty commonly used system in high-speed experimental aerodynamics. A typical schlieren system will shine a collimated light source on the target (a wind tunnel test section or, above, a candle), bounce that light off a mirror, block half the light with a knife-edge at the focal point, and then record…
Convection in Cream and Liqueur
We are used to associating convection with differences in temperature, but what’s actually necessary for a Rayleigh-Taylor-type instability is a density variation (and a gravitational field). The solutal convection seen above when mixing liqueur with cream is caused by the interaction of density and surface tension. When the alcohol of the liqueur mixes with the…
The White Hole in Your Sink
Ever notice the distinctive ring that forms in your kitchen sink when you turn the water on? This phenomenon is known as a hydraulic jump; it occurs when a fast moving fluid (the water just discharged from the faucet) runs into a slow moving fluid (the water that’s been sitting in the sink) and transfers…