AFRL completes Subsonic Swept-Wing Laminar Flow Flight Test
By Holly Jordan, AFRL Air Vehicles Directorate
/ Published December 07, 2006
WRIGHT-PATTERSON AIR FORCE BASE, Ohio -- Turbulent air flow over an air vehicle wing surface increases airfoil drag and inhibits efficient flight. In an effort to reduce this problem, the Air Force Research Laboratory recently completed the Subsonic Swept-Wing Laminar Flow Flight Test (SWIFT).
AFRL researchers completed SWIFT flight testing to investigate span-wise periodic discrete roughness element (DRE) technology for maintaining wing laminar flow. DREs are small bump-like or dimple-like structures designed to reduce drag by controlling instabilities and inhibiting transition from laminar to turbulent air flow. The use of DREs could cut down on fuel consumption and increase range or time-on-station for future aircraft. DRE technology could potentially be used for the SensorCraft concept, a high-altitude long-endurance surveillance aircraft.
During the testing, engineers collected data from a swept-wing test article mounted on a Cessna test bed aircraft. Testing the swept wing section in flight, as opposed to in a wind tunnel, allowed researchers to study the wing in an environment that was more representative of the actual SensorCraft flight environment. The test results are promising that the DREs could be used to push the transition of the boundary layer between laminar and turbulent flow further back on the wing, thus minimizing drag and allowing more efficient flight.
The data generated from the testing will validate computational fluid dynamics predictive codes. The test results confirmed the viability of DRE technology for application to the SensorCraft concept, but further maturation of the technology with the boundary layer flow physics is warranted.