Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
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Holiday Fluids: Santa’s Aerodynamics
Today we have some holiday-themed fluid dynamics: visualization of flow around Santa’s sleigh! This is a flowing soap film visualization at a low speed (author Nick Moore has some other speeds as well). Santa’s sleigh is what aerodynamicists call a bluff body–a shape that is not streamlined or aerodynamic–and sheds a complicated wake of vortices.…
Holiday Fluids: Snowflakes
Just about everyone wishes for a White Christmas, but even when that happens, it’s rare to get a good look at the beauty of individual snowflakes. Alexey Kljatov’s macro photography of snowflakes is simply stunning and highlights the incredible variety of forms snowflakes take. A snowflake forms when a water droplet freezes onto dust or other…
Holiday Fluids
BYU Splash Lab–those breakers of bottles, skippers of rocks, spinners of eggs, students of soap films, masters of splashes, and all-around cool fluid dynamicists–have some fluids-themed, high-speed holiday greetings. Likewike, here at FYFD we’ll be spending the next week celebrating the physics and fluid dynamics of the winter holiday season! In the meantime, you can…
Shuttle Re-Entry
Complicated shock wave patterns envelope vehicles traveling at supersonic and hypersonic speeds. A shock wave is essentially a very tiny region–only a few mean free path lengths wide–over which flow conditions, including density, pressure, velocity, and temperature, change drastically. The image above shows a model of the Space Shuttle at a re-entry-like, high angle of attack at around Mach 20 in one of…
Huddling Penguins and Traffic Jams
Male emperor penguins have the unenviable task of incubating their eggs in temperatures as cold as -50 deg Celsius and winds of up to 200 km/h. To stay warm, the penguins form huddles of up to thousands of individuals. Observations in the wild show that these huddles move in a stop-and-go fashion, with changes propagating…
Collapsing Soap Bubbles
The colors of a soap film are directly related to their thickness. If a film becomes thin enough (~10 nanometers), it appears black. (Here’s why.) This video shows the thinning of a vertical soap film. Normally, this is a linear process, with gravity pulling the fluid downward and progressively thinning the film from top to bottom at a constant rate. At…
Reader Question: What is Surface Tension?
Last week reader thesnazz asked: Is there a difference between surface tension and viscosity, or are they two manifestations of the same process and/or principles? If you know a given fluid’s surface tension, can you predict its viscosity, and vice versa? I’m tackling this one in parts, and you can click here to read about…
Reader Question: What is Viscosity?
Reader thesnazz asks: Is there a difference between surface tension and viscosity, or are they two manifestations of the same process and/or principles? If you know a given fluid’s surface tension, can you predict its viscosity, and vice versa? This is a good question! To answer it, let’s think about where surface tension and viscosity come from. Like many…
Bullet Through a Bubble
A bullet passes through a soap bubble in the schlieren photo above. The schlieren optical technique is sensitive to changes in the refractive index and, since a fluid’s refractive index changes with density, permits the visualization of shock waves. A strong curved bow shock is visible in front of the bullet as well as weaker lines marking additional shocks waves around the bullet. Impressively,…
Fluctuating Ferrofluids
https://youtu.be/MU7wiveVCbg Ferrofluids–liquids seeded with magnetically sensitive ferrous nanoparticles–demonstrate some beautiful and bizarre behaviors when exposed to magnetic fields. This video shows the reaction of a pool of ferrofluid to the magnetic field generated by an alternating current through a simple wire coil. At 1 Hz, the fluid response is not unlike the normal-field instability–the characteristic…