Ask OCE — February 24, 2006 — Vol. 1, Issue 5

Three Langley Research Center engineers conducted a wind tunnel investigation that extended the existing knowledge base for supersonic transports. In “Off-Design Reynolds Number Effects for a Supersonic Transport,” published in the November-December 2005 Journal of Aircraft (Vol. 42, No. 6), Lewis Owens, Richard Wahls, and Melissa Rivers examined the effects of high Reynolds numbers on scale models of a High Speed Civil Transport aircraft (HSCT).

The Reynolds number is the ratio of inertial to viscous forces in the flow and can sometimes affect what the vehicle experiences in different flow fields. Engineers can utilize a smaller scale (less expensive) model of a particular aircraft concept and test its aerodynamic capabilities in the lab while matching the flight Reynolds number of the actual full-scale vehicle. Testing for Reynolds number effects allows researchers to develop better flow modeling to help improve their abilities to predict the full-scale vehicle performance.

The recent tests included longitudinal and lateral/directional studies at both transonic speeds and subsonic high-lift conditions across a range of Reynolds numbers approaching flight conditions. Owens, Wahls, and Rivers conducted their research in the National Transonic Facility at Langley Research Center as part of NASA’s High Speed Research Program.

“Having access to unique test facilities like the National Transonic Facility helps us to understand the roles that flow boundary layer development and flow separation have on the aerodynamics of vehicles,” Owens said. “Experiences like the ones gained in the High Speed Research Program continue to move us toward the goal of someday predicting the impact these flow phenomena have on vehicle performance.”

Since the mothballing of the Concorde SSTs, there has been momentum building for the introduction of a new class of supersonic passenger transport aircraft. A new efficient and environment-friendly supersonic aircraft would likely cut in half the ten-hour travel time from London to Tokyo. The Langley teams research is instrumental for the effective research and development of the next generation of supersonic civil aviation aircraft.

Connect to the NASA Library to access the Journal of Aircraft.