Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Supercell Thunderstorm
Photographer Mike Olbinski has captured a spectacular timelapse of a supercell thunderstorm over the plains of Texas. Supercells are characterized by a strong, rotating updraft known as a mesocyclone, seen clearly in the video. These storms are commonly isolated occurrences, forming when horizontal vorticity in the form of wind shear is redirected upwards by an…
Reader Question: Does Flow Viz Alter Flow?
Reader gorbax asks: I’ve been wondering for a while, actually, how do we know when the method of flow visualization doesn’t actually alter the flow of a fluid itself? This is a great question and one that fluid dynamicists have to deal with all the time. Ideally, we’d love to measure everything we want from…
Visualization Via Temperature
One downside to many flow visualization techniques, like those using dye, smoke, or particles, is the difficulty of dealing with their aftermath. You can only introduce so much of them into a wind or water tunnel before it’s necessary to shutdown and clean everything. One alternative is to use temperature, as shown in the video…
Fluids Round-up – 9 June 2013
It’s time for some more fluidsy fun around the Internet! Here are some fun links I’ve come across since our last round-up. NPR reviews how dolphins and others play with vortex rings. Lawrence Berkeley National Laboratory/UC Berkeley offer some insight into simulating bubbles popping. (Hint: it requires supercomputers.) FlowViz shares some awesome accidental Rayleigh-Taylor instabilities you can replicate at…
Visualizing F-18 Flow
Flow visualization techniques are helpful outside of wind and water tunnels, too. The photo above comes from the F-18 High Alpha Research Vehicle (HARV) program in which techniques like smoke and dye visualization were used in-flight to visualize airflow around an F-18 at large angles of attack. During flight a glycol-based liquid dye was released from tiny…
Droplets Within Droplets
This video shows a multi-layered droplet, in which several droplets are formed one inside the other as an initial drop falls through a layer of oil sitting atop another liquid. When the drop falls, its potential energy gets transformed into interface energy, creating a fascinating interplay of surface tension, deformation, and miscibility between the fluids.…
Dye Droplet
A drop of fluorescent dye falling into quiescent water forms fantastical structures that are a mixture of vorticity, turbulence, and molecular diffusion. The horseshoe-like shape near the front of the drop is a typical shape for two fluids strained by moving past one another. The main section of the drop billows outward like a parachute,…
“Levitating Water”
Al Seckel, a cognitive neuroscientist and expert on illusions, created this “Levitating Water” installation, in which multiple streams of water appear as a series of levitating droplets thanks to a strobing light. The well-timed strobe lighting tricks the brain into seeing many different falling droplets as the same, nearly stationary droplet. The effect is similar…
Droplet Bounce
This high-speed video shows the remarkable resilience of a water droplet upon impact against as a solid surface. The droplet deforms into a pancake-shape, with its center depressing almost flat before rebounding upward. The rest of the drop follows, splitting into several droplets as capillary waves dance across its surface. When one satellite drop almost…
Incense in Transition
A buoyant plume of smoke rises from a stick of incense. At first the plume is smooth and laminar, but even in quiescent air, tiny perturbations can sneak into the flow, causing the periodic vortical whorls seen near the top of the photo. Were the frame even taller, we would see this transitional flow become…