January 28, 2010—Ripples in soap film mimic the flow of air from a hand-held fan in an award-winning image from the American Physical Society's (APS) most recent Gallery of Fluid Motion.
To create the image, a team at the Technical University of Denmark flapped a rigid foil over soap film, creating a breeze that made the film flow into a "beautiful butterfly shape," according to the scientists. (Related pictures: "Best Microscopic-Life Images of 2009 Named.")
Each year the APS Division of Fluid Dynamics sets up the Gallery of Fluid Motion exhibit at its annual meeting. The exhibit displays "stunning graphics and videos from computational or experimental studies showing flow phenomena," according to the APS Web site. A panel of referees then selects the most outstanding entries for their artistic content, originality, and ability to convey information. The winners are published in the journal Physics of Fluids.
The above image, along with four other winners, was on display at the Minneapolis Convention Center from November 22 to 24, 2009.
Image courtesy Teis Schnipper, DTU, via APS
Bubbles "deformed" by bumping into their neighbors star in one of five pictures named the best fluid-motion images of 2009 by the American Physical Society.
In such an array, the pressure of the air in the central bubbles is almost the same as that of the surrounding liquid. This allows the bubbles to grow larger before collapsing. But outer bubbles almost immediately burst due to the greater pressure of the surrounding liquid.
When this image was taken—six microseconds after the laser's impact—bubbles on the edges of the image were already collapsing, while bubbles at the center had almost reached their biggest sizes.
Image courtesy Cavitation Lab, SPMS Nanyang Technological University, via APS
"Wine Glass" Droplet
A three-millimeter-wide oil droplet hits rubbing alcohol to form an upside-down "wine glass" in one of the American Physical Society's best fluid-motion pictures of 2009.
The image, created by a team at the Massachusetts Institute of Technology, was captured by projecting light onto the droplet from both sides. Oil and alcohol bend light differently, so the oil droplet's edges appear bright.
Because oil is denser than rubbing alcohol, the droplet fell through the alcohol to create the unusual shape. But oil is also soluble in alcohol, and the droplet dissolved as it fell.
Image courtesy R. R. La Foy, J. Belden, A. M. Shih, T. T. Truscott, & A. H. Techet via APS
Resembling a river valley seen from the air, this two-dimensional, computer-generated picture—one of the American Physical Society's best fluid-motion images of 2009—illustrates what's known as a von Kármán vortex street.
Named after Hungarian aerodynamicist Theodore von Kármán, a vortex street occurs when an airstream flows around a body—in the above image, a hollow cylinder—and breaks behind it into a series of wakes and eddies.
Image courtesy Jens Kasten Christoph Petz Ingrid Hotz Gilead Tadmor, Bernd R. Noack, Hans-Christian Hege via APS
One of the hazards of modern flight takes shape in an award-winning picture from the American Physical Society's 2009 Gallery of Fluid Motion.
In flight, an airplane's wingtips create a counter-rotating pair of vortices—pockets of circulating air that get forced down underneath the plane's wings. These primary vortices can create secondary vortices when they interact with the ground. The vortices present a potential danger to other aircraft during flight.
Now, a Cornell University team has developed a new technique to visualize the vortices: Using a pair of flaps to simulate aircraft wings, the team pooled dye on the ground and used lasers to make the swirls of fluid glow.
In the above image, the primary vortices are seen as red circles, and the secondary vortices are the lime-green swirls. The mirror image in the lower half of the photo is a reflection on the ground.
Image courtesy Harris, Miller & Williamson via APS