Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
High-Speed Ferrofluid
High-speed video captures the behavior of a ferrofluid trapped between two magnets. Ferrofluids contain tiny ferromagnetic particles suspended in a carrier fluid like oil or water. The distinctive peaks and valleys of a ferrofluid subject to a strong magnetic field is due to the normal-field instability and is a result of the fluid minimizing its…
Diesel Ignition
In a diesel engine, ignition of the injected fuel occurs due to the heat caused by the compression of the fuel/air mixture. (In petrol/gasoline engines, spark plugs are used for ignition.) The subsequent expansion of gases drives the pistons of the engine downward, creating mechanical energy. This high-speed video shows the in-cylinder combustion within a…
Playing Pac-Man with Water Droplets
The vibrations of a plate in the horizontal and vertical directions can be used to control the motion of a drop placed on the surface. Here a droplet of water on a superhydrophobic surface is controlled by joystick a la Pacman. For more, see papers here and here.
Viscous Fingers
A Hele Shaw cell is little more than two glass plates separated by a thin layer of viscous fluid. The cell serves as a good test bed for viscous, low Reynolds number flows such as those found in microfluidics. Here a less viscous fluid is injected into the center of the cell, causing the finger-like protrusions of…
Visualizing Fish Wakes
This novel flow visualization technique uses dilute solutions of the tobacco mosaic virus (TMV). These rod-shaped particles align with shear and produce a birefringent interference pattern visible when viewed between crossed polarizing filters. The intensity of the light is related to the magnitude of shear. The technique is benign to the fish but enables researchers…
The Disintegrating Bowl
A viscous fluid droplet impacts a thin layer of ethanol, which has a lower surface tension than the viscous fluid. A spray of tiny ethanol droplets is thrown up while a bowl-shaped crown of the viscous fluid forms. As the ethanol droplets impact the bowl, the lower surface tension of the ethanol causes fluid to…
Mapping Flames
Combustion remains a fascinating and only partially understood phenomenon. Here scientists work to map a flame in three dimensions using high-speed cameras and digital reconstruction. (submitted by Chi M)
Making Waves
A standing wave is created in a wave tank by fixing a wall at one end and moving the other wall–the wave generator–at a frequency such that the outgoing waves are superposed on those reflecting back from the wall. This doubles the amplitude of the wave. In the standing wave (also called clapotis), the surface…
Jump Rope Aerodynamics
Researchers have used high-speed video and numerical simulation to capture the effects of aerodynamics on jump roping. After videoing an athlete jumping rope and constructing a jump roping robot (shown above imaged multiple times with a strobe light), they found that the U-shaped tip of the jump rope bends away from the direction of motion.…
Airfoil Soap Flow
A flapping airfoil in a vertically flowing soap film produces six vortices per cycle. The vortices form a pattern of two vortex pairs separated by vortex singlets. In the wake of the foil, they advect relative to one another due to their mutual influence, as if dancing. #