Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Vapor Cone
This stunning National Geographic photo contest winner shows an F-15 banking at an airshow and a array of great fluid dynamics. A vapor cloud has formed over the wings of the plane due to the acceleration of air over the top of the plane. The acceleration has dropped the local pressure enough that the moisture…
Liquid Lenses
Here astronaut Andre Kuipers demonstrates fluid dynamics in microgravity. A roughly spherical droplet of water acts as a lens, refracting the image of his face so that it appears upside down. The air bubble inside the droplet refracts the image back to our normal perspective again. (Photo credit: Andre Kuipers, ESA; via Bad Astronomy)
The Backward-Facing Step
This photo collage shows vortices shed off a backward-facing step. The flow is left to right. Here the flow is visualized using dye released in water. Initially, the vortex forms near the bottom of the step in the recirculation zone. Because flow over the top of the vortex is much faster than the flow beneath…
Homemade Hybrid Rocket Engine
In this video, Ben Krasnow details and demos a small hybrid rocket engine he built in his workshop. Hybrid rockets utilize propellants that are two different states of matter, in this case gaseous oxygen as the oxidizer and solid acrylic as the fuel. Krasnow’s verbal explanation of a convergent-divergent nozzle, used to accelerate flow to…
Atomizing
High-speed video reveals the complexity of fluid instabilities leading to atomization–the breakup of a liquid sheet into droplets. A thin annular liquid sheet is sandwiched between concentric air streams. As the velocity of the air on either side of the liquid sheet varies, shear forces cause the sheet to develop waves that result in mushroom-like…
Shark-Tooth Instability
A viscous fluid inside a horizontally rotating circular cylinder forms a shark-tooth-like pattern along the fluid’s free surface. This is one of several patterns observed depending on the fluid’s viscosity and surface tension and the rotational rate of the cylinder. (Photo credit: S. Thoroddsen and L. Mahadevan; for more, see Thoroddsen and Mahadevan 1996 and…
Formula 1 Aerodynamics
[original media no longer available] Computational fluid dynamics (CFD) and the advent of supercomputing have forever changed the way engineers design. Here the use of CFD in the design of Formula 1 racing cars is discussed. Although CFD is used by many companies in place of wind tunnel testing, each method has its advantages. CFD…
Acoustic Levitation
Researchers at Argonne National Laboratory are using acoustic levitation of droplets to further pharmaceuticals. By placing two precisely aligned speakers opposite one another, a standing wave can be created. At nodes along the standing wave, there is no net transfer of energy, but the acoustic pressure is sufficient to cancel the effect of gravity, allowing…
Ferrofluid Drop
A drop of ferrofluid is shaped by seven small circular magnets sitting beneath the glass and paper. Ferrofluids are made up of nanoscale ferromagnetic particles suspended in a carrier liquid. Under the influence of magnetic fields, they can take on fantastic shapes, including sharp-tipped droplets and labyrinthine mazes. This image is taken from the National…
Boiling Without Bubbles
Water droplets sprinkled on a sufficiently hot frying pan will skitter and skate across the surface on a thin layer of vapor due to the Leidenfrost effect. When a solid object is much warmer than a liquid’s boiling temperature, the surface is surrounded by a vapor cloud until the solid cools to the point that…