Alternative to Wind Tunnels: Computer Models

DAYTON, Ohio — Aeronautical researchers at Wright-Patterson Air Force Base have found that they can use computer models to test aircraft designs at about one-tenth the cost of using wind tunnels.

Since the days of the Wright brothers, researchers have used wind tunnels to test airframe designs by subjecting scale models to airflow examinations.

Now, a research group led by Joseph J. S. Shang at Wright-Patterson’s Aeronautical Systems Division is using a hookup to a National Aeronautics and Space Administration computer in California to do the tests in less time and more cheaply.

Recently, Shang’s group simulated a flight of the X-24C, an old Air Force aerospace research vehicle, at six times the speed of sound. The Air Force had conducted wind tunnel tests on the X-24C’s airframe in 1974, and the data was still available for comparison.

Shang said his researchers had found differences of only 2% to 5% when they compared their findings with the original wind tunnel results.

He said the X-24C wind tunnel tests would cost $500,000 today. The computer simulation cost $56,000, and Shang said the price decreases as his group improves the technology.

The complex computer program needed for the tests must be able to simulate the interaction of shock waves that develop around an airframe moving at six times the speed of sound.

It resembles a video game. Colorful graphics show airflow patterns and gradations of temperature and pressure on the aircraft’s surface. Researchers can also look at cross-sections of the aircraft and the surrounding airflow, something that cannot be done in a wind tunnel.