Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Cloud Streets
Cloud streets–long rows of counter-rotating air parallel to the ground in the planetary boundary layer–are thought to form as a result of cold air blowing over warm waters while caught beneath a warmer layer of air, a temperature inversion. As moisture evaporates from the warmer water, it creates thermal updrafts that rise through the atmosphere…
Rocket Engine Testing
Rocket engine tests usually feature a distinct and steady pattern of Mach diamonds in their exhaust. This series of reflected shock waves and expansion fans forms as a result of the exhaust pressure of the rocket nozzle being lower or higher than ambient pressure. A rocket will be most efficient if its exhaust pressure matches…
Water Spray from a Tire
The spray thrown up by a rolling tire is simulated in the lab by running a single-grooved tire (top) against a smooth tire (bottom) that simulates the road. A supply of water flows from the left at the speed of the rolling tires (6 m/s). The resultant sheet of water is a familiar site to…
Bill Nye Demos
[original media no longer available] Have a little science enthusiasm from Bill Nye to brighten your Tuesday! This video includes demonstrations on thermodynamics (sucking the balloon into the flask), the Marangoni effect (driving the powder off the water surface and powering the glue boat by creating gradients in surface tension), and buoyancy (floating cans of…
Shear-Thickening Oobleck
Oobleck is a commonly utilized fluid in demonstrations of non-Newtonian behavior. Rather than being linearly viscous with respect to shear, oobleck is shear thickening, meaning that it becomes more viscous the more that it is sheared. This is what causes crazy formations when it’s vibrated, makes it useful as liquid armor, and enables people to…
Atomization
Atomization–breaking a flowing liquid into a fine spray–is important for fuel injection in a variety of engines, including automobiles, jet engines, ramjets, scramjets, and rockets. The more effectively a liquid fuel can be dispersed as a spray in an engine, the more efficient and stable the combustion will be. The apparatus in this high-speed video…
Fishbone Jet Collision
The collision of two jets of radius 420 μm results in a fishbone-like structure. The fluid contains a dilute polymer mixture whose viscoelastic effects resist the tendency of the droplets to detach from the ligaments. The breakup of the jets into droplets is important for applications in inkjet printing. The photo has been rotated 90-degrees…
Microgravity Water Spheres
Here astronaut Don Pettit demonstrates the effects of rotation on a sphere of water in microgravity. Bubbles, being less dense than water, congregate in the middle of the sphere along its axis of rotation. Tea leaves, which are denser than the water, are thrown to the outside; this is the same concept used in a…
Guinness Physics
Take a look at the physics of a pint of Guinness, including the formation of foam, the circulation of bubbles, and the importance of nitrogen and surfactants. The Physics of Fluids paper the host refers to is available here. (And, yes, I will admit to debating the physics occurring in my pint glass while in…
Fluid Sculpture
Droplet collisions captured instantaneously create beautiful fluid sculptures that, though common, are too fast for the human eye. Here a bubble was blown onto the surface of the fluid, then a droplet was released to fall into the center of the bubble, bursting it. As that droplet rebounded in a Worthington jet, a second droplet…