Blast! Drag! A New Plane! From a Giant Wind Tunnel

Windy City facility helps design cars, ships, missiles

THINK science is a drag? Then meet the faculty of the mechanical and aerospace engineering department at the Illinois Institute of Technology. They could not agree with you more.

In fact, the professors are so fascinated by drag that they recently started up a wind tunnel faster for its size than any other in the country. The 2,000-horse-power engine churns out a blast of up to 550 miles per hour.

Scientists and research engineers will use the $4-million facility to find ways to reduce the drag on plane wings, fuselages, missiles, trains, cars, and other types of vehicles and structures.

Research with the tunnel and its 16-foot fan will probably inspire changes in aerodynamic design that can increase fuel efficiency and durability to save millions of dollars for airlines and other industries, scientists say.

The National Diagnostic Facility, as the tunnel is officially known, will also help upgrade United States weaponry.

For example, the tunnel could enable the Pentagon to design better missiles, increase the maneuverability of aircraft like the stealth jet fighter, and alter the telltale wakes of warships. The United States Department of Defense provided most of the funding for the institute's project.

The advent of a wind tunnel of unrivaled power and size will enable inventors to prove the feasibility of many blue-ribbon discoveries that otherwise would remain on the shelf, says Hassan Nagib, chairman of the department of mechanical and aerospace engineering.

``In the past, many innovative ideas have not been given a chance to mature into something that is put into practice'' both for industry and defense, he says.

The tunnel is especially valuable for research because of its size and comparatively low level of turbulence, says Valdis Kibens, a scientist at McDonnell Douglas Aircraft Co. in St. Louis. A steadier flow stream helps researchers to better determine how to reduce drag around an object.

Moreover, the tunnel will offer hands-on insights unrivaled by the most sophisticated supercomputers. No computer can handle the chaos and complexity of flow streams at high velocities, says Thomas Corke, a professor of mechanical and aerospace engineering at the institute.

``As powerful as computers are now, they are still two or three computer generations away from being able to do the problems completely,'' Dr. Corke says.

The Air Force plans in June to launch the first research project in the tunnel by testing a model of a stealth jet fighter, says Dr. Nagib.

The Air Force has designed a fighter that skirts radar detection but lacks the high degree of lift that makes for a maneuverable combat plane. The tunnel will help military researchers determine how to maximize the upward force of air on the wings, Corke says.

The Pentagon also might use the tunnel in an effort to eliminate a menacing aerodynamic glitch in the Tomahawk cruise missile, the self-guided weapon most recently fired from warships and planes against Iraqi targets during the Persian Gulf War.

During launching, and soon after the ignition of its rocket booster, the Tomahawk sometimes rears too far upward. A missile malfunctioning in such a way might shoot down the aircraft that launches it, Corke says.

The Navy plans to use the wind tunnel according to the same principles observed in the use of an experimental water tank. After accounting for the differences in moving air and water, the Navy will test how a cylindrical pole oscillates when exposed to a high speed flow.

The findings could lead to a better design for an undersea cable, drilling pipe, or ship's bow, according to Corke.

The Navy also plans to use the tunnel to study ship wakes. The trails can persist in the ocean for hours, offering adversaries equipped with satellite intelligence clues to a vessel's type and course.

Using the tunnel, naval researchers could devise a new hull design that masks the identity of warships. When applied to all ships, the design would ensure all types of vessels leave wakes of the same shape, says Corke.

The tunnel will offer an edge in commercial as well as military conflict. Institute scientists plan to continue research into narrow rings that they have been used to encircle an aircraft fuselage and reduce turbulence. The concentric rings, attached just off the metal skin of the fuselage, cut drag by 3 percent, according to Corke.

Moreover, successful research on increasing the lift of commercial aircraft could mean more sales for US aircraft makers and better fuel efficiency for airlines.

It would also shorten the required runway length for planes, thereby enabling cramped cities with comparatively small airports to handle larger planes, says Nagib.

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