Scaled Model Testing of Rotor Hub Root-End Airfoil Shapes

In order to extend the boundaries of helicopter performance and increase forward-flight speed, it is necessary to reduce the drag on the rotor hub, which can account for as much as 30% of the total parasite drag on the helicopter. Currently, there is limited experimental data available to predict the drag force on new hub configurations. The purpose of this testing is to create a database of lift and drag at various angles of attack to aid in hub design and hub drag prediction. Testing was conducted in the 12 inch-diameter water tunnel at ARL Penn State on four shapes - DBLN 526, 4:1 Ellipse, 3.25:1 Rectangle, and a new Optimized Cambered Shape (OCS) designed at UT Knoxville. Load cell data for lift and drag were obtained for angles of attack from approximately -5 degrees to 5 degrees. Drag data were also calculated using PIV velocity fields. Results are plotted and tabulated for use in future hub drag prediction toolsets.