The
sight was eerie, no doubt. In the dead of night last summer in
the middle of Utah's Great Salt Lake Desert, a theatrical fog
machine pumped out a steady stream of white smoke while technicians
zapped it with green laser light and videotaped the swirls and
eddies. What may have looked like special-effects filming for
a science-fiction movie was in truth an experiment to determine
science fact. Specifically it was to understand high-speed air
turbulence, which is of interest to airplane designers, among
others.
High-speed air turbulence is difficult to study, Notre Dame
Assistant Professor of Aerospace Engineering Scott Morris explains,
because the faster the air flows the more the boundary area of
turbulence shrinks in height. In traditional lab wind tunnels,
that region of turbulence can be minuscule. But if you had a very,
very large wind tunnel, the region would be proportionally larger
and easier to analyze. Slower speeds of flow could simulate high-speed
turbulence.
That in a nutshell is why Morris and his research team have
traveled to the U.S. government's Dugway Proving Ground in the
Utah desert for the past several summers. "This particular site
west of Salt Lake City is a unique environment," he says. "It
is a remarkably smooth area, said to be one of the few places
on Earth where you can actually see the curvature of the planet
on land. It's nestled in between two mountain ranges, and in the
summer each evening a breeze comes out of the north, creating
a huge wind tunnel."
Last summer's experiment confirmed a long-standing theory, previously
observed only in the lab, that swirls of turbulence are organized
in wedge shapes, like tiny ramps near the surface. "What we've
proven is that in nature, you see these ramp structures all of
the time," Morris says.
Photo from Scott Morris
(July 2005)
