AFRL Finding Ways to Decrease Unmanned Air Vehicle Costs

In support of the Aeronautical Systems Center's (ASC) Global Hawk Systems Group, AFRL has undertaken a program to study manufacturing tolerances for laminar flow on aircraft wings. On the drawing board, air vehicle designs have perfectly smooth aerodynamic surfaces, yet it is nearly impossible for manufacturers to fabricate those surfaces without some imperfections. Any surface imperfection, no matter how slight, can affect the properties of the boundary layer— the air flowing nearest an air vehicle's body during flight. In turn, this airflow dramatically impacts the amount of drag an air vehicle experiences. When the boundary layer is smooth, or laminar, drag is minimal; as the boundary layer becomes more turbulent, drag increases. Nonetheless, decreasing the amount of surface imperfection is not always a practical solution, because as the manufacturing processes become more stringent, they also become increasingly expensive and time-consuming endeavors. It is therefore vitally important to determine the relationship between the height, shape, and location of surface imperfections and the resulting performance degradation.