AFRL COMPLETES SUBSONIC SWEPT-WING LAMINAR FLOW FLIGHT TEST Published Dec. 11, 2006 By Plans and Programs Directorate AFRL/XP WRIGHT-PATTERSON AIR FORCE BASE, Ohio -- Turbulent airflow over an air vehicle wing surface increases airfoil drag and inhibits efficient flight. In an effort to reduce this problem, AFRL researchers completed a subsonic swept-wing laminar flow flight test (SWIFT) to investigate spanwise periodic discrete roughness element (DRE) technology for maintaining wing laminar flow. DREs are small, dimple- or bumplike structures designed to reduce drag by controlling instabilities and inhibiting transition from laminar to turbulent airflow. The use of DREs can cut fuel consumption and increase range or time on station for future aircraft. DRE technology has potential application to the SensorCraft concept, a high-altitude, long-endurance surveillance aircraft. During the SWIFT effort, 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 enabled the researchers to study the wing in an environment more representative of the SensorCraft's actual flight environment. The test results support the idea that DRE technology has use in pushing the boundary layer's transition from laminar to turbulent flow further back on the wing, minimizing drag to permit more efficient flight. While the data generated from the testing validates computational fluid dynamics predictive calculations and confirms the viability of DRE technology for application to the SensorCraft concept, further maturation of the technology with associated boundary layer flow physics is warranted. AFRL is continuing this line of research through the Air Force Office of Scientific Research.