Science is about to take a big step forward, a step that will bring money and prestige to Oregon. The National Science Foundation has recently awarded University of Oregon physicist Russell J. Donnelly $5 million, the largest grant ever made to a single UO investigator. Under Donnelly's supervision, a group of scientists will use the money to build, test, and refine a prototype "cryostat," an experimental device similar to a giant Thermos bottle filled with extremely cold, gaseous helium and outfitted with an array of high-technology sensors.
When cooled to about 450 degrees below zero, just above the point at which helium liquefies, the element behaves in unusual ways. Experiments performed in the cryostat will tell scientists new things about turbulence and convection--and could lead to safer airplanes and improved automobile gasoline mileage.
Carefully controlled studies at this temperature can answer important questions about intense convection (circulatory motion), the turbulence (irregular currents) that develop around moving objects. This information will provide a previously unavailable window into the physics of movement and could solve problems that have bedeviled physicists for decades.
"This device will multiply the range of turbulent intensities attainable in the laboratory by a factor of a thousand," Donnelly says.
Using helium in devices like wind tunnels will have many applications, from basic research to product testing. For example, a cryogenic chamber could be used to test the way air flows over the wing of a proposed aircraft, Donnelly explains.
In simplified terms, physicists use a number, called the Reynolds number, to represent turbulence. Technical limitations have kept scientists from creating wind-tunnel conditions--where scale models of new designs are tested for safety and efficiency--with Reynolds numbers much higher than 10 million. This is a problem, since the wind flowing over the wing of a jet in flight has a Reynolds number of about 70 million.
"Obviously jets still fly," Donnelly says, "because engineers are quite clever and have good intuition, but they do not know experimentally how a full-sized version of one of their designs will fly until it is actually built."
Donnelly's cryostat will achieve Reynolds numbers of 100 million.
The research project will be the heart of the Oregon Cryogenic Turbulence Center to be housed on the University of Oregon campus, where Donnelly has conducted research for thirty years.
This three-year grant will allow Donnelly and his colleagues to develop the instrumentation they need to observe turbulent flows at very low temperatures and to perform new experiments that will make possible conditions never before attained in the laboratory.
Once Donnelly's team refines the one meter (3.3 feet) tall prototype tank, a scaled-up 10-meter version is envisioned for construction-using additional funding--at a National Turbulence Center to be built at the Brookhaven National Laboratory on Long Island, New York. The full-sized tank will achieve Reynolds numbers of 10 billion--comparable to the turbulence that takes place on the surface of the sun.
The location at Brookhaven takes advantage of the existence there of the world's largest helium liquefier. Plans call for the facility at Brookhaven to house a wind tunnel that uses liquid helium instead of air and a long, horizontal tank partly filled with liquid helium for testing the drag forces that affect surface ships.
"These and other related research tools would multiply the practical applications of this basic research project enormously," Donnelly notes. "Building the prototype here at the University of Oregon is a vital first step."