Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Impinging Without Coalescing
Three impinging jets of silicone oil rebound without coalescence due to thin-film lubrication between the jets. The motion of the oil replenishes the thin layer of air separating the streams. The same phenomenon keeps droplets from coalescing as well. (Photo credit: BIF Lab, Department of Engineering Science and Mechanics, Virginia Tech) #
Blast Waves
[original media no longer available] Watch closely in this high-speed video of a bomb exploding and you will see the spherical blast wave moving outward as a visual distortion. The increase in temperature caused by the leading shockwave changes the index of refraction of the air, bending the light and distorting our view of the…
2D Convection
This simulation shows 2D Rayleigh-Benard convection in which a fluid of uniform initial temperature is heated from below and cooled from above. This is roughly analogous to the situation of placing a pot of water on a hot stovetop. (In the case of the water on the stove, the upper boundary is the water-air interface,…
Reader Question: Faucet Physics
jessecaps-blog-deactivated20170 asks: With respect to the laminar/turbulent flow in the faucet, at the end he explains that the diameter is smaller inside the valve compared to the nozzle and therefore the velocity is greater and turbulence is achieved there before it leaves the nozzle. But turbulence is characterized by the Reynolds number not the velocity, so…
Laminar and Turbulent Flows from a Faucet
Here laminar and turbulent flows, basic concepts in fluid mechanics, are demonstrated in the kitchen sink! While laminar flow is often desirable for decreasing drag due to friction, most practical flows are turbulent. The hissing the video author associates with the onset of turbulence is not a coincidence either. The chaotic motion of turbulent flows can…
Disrupting the Coalescence Cascade
When a droplet contacts a pool, a thin layer of air can get trapped beneath the droplet, delaying the instant when the liquids contact and surface tension pulls the droplet into the pool. If the pool is being vibrated, air flows more easily into the gap, keeping droplets intact longer. It’s even possible to make…
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…