Circulation Control as a Roll Effector for Unmanned Combat Aerial Vehicles

This paper reports on a numerical investigation of the use of trailing-edge circulation control as a roll effector on a generic unmanned combat aerial vehicle: the DLR-F19 stability and control configuration. The Coanda effect induced by fluidic injections at the trailing edge of a wing is used to increase circulation and generate lift. Reynolds-averaged Navier-Stokes predictions are validated against wind-tunnel experiments conducted at the Georgia Institute of Technology and NASA's basic aerodynamic research tunnel on an airfoil employing trailing-edge circulation control. Two turbulence models are used: the Wilcox k-omega model and Menter's shear-stress transport, showing that the Wilcox k-omega model provides the best comparisons with the experimental data. Baseline data for the stability and control configuration with conventional control surfaces from wind-tunnel experiments done at the low speed wind-tunnel owned by the German- Dutch Wind Tunnels foundation (DNW-NWB) are used to ensure the correct flow features are being modeled for the flows encountered by this type of unmanned combat aerial vehicle and to provide a comparison for the performance of the circulation control devices. Modifications have been made to the DLR-F19, replacing the conventional control surfaces with trailing-edge circulation control of the same spanwise extent. This includes two configurations: one with a single slot, and one with three slots of equal width along the wing. The circulation control performs well at low angles of attack, producing a similar roll moment to the conventional control surfaces. Due to the flow separation at the high angles of attack, the circulation control is unable to generate a rolling moment. Finally, the flow topology is examined to understand the causes of the decrease in the performance.