Type of Document Master's Thesis Author Graf, Will Edward URN etd-05262005-170916 Title Effects of Duct Lip Shaping and Various Control Devices on the Hover and Forward Flight Performance of Ducted Fan UAVs Degree Master of Science Department Aerospace and Ocean Engineering Advisory Committee
Advisor Name Title Mason, William H. Committee Co-Chair Ng, Fai Committee Co-Chair Devenport, William J. Committee Member Keywords
- control effectors
- ducted fan
- duct lip shaping
- stabilizer vanes
- control vanes
Date of Defense 2005-05-13 Availability unrestricted Abstract
The military's desire for ducted fan vertical takeoff and landing (VTOL) unmanned aerial vehicles (UAVs) stems from the vehicles' relatively small size, safety in tight quarters, increased payload capacity for their size, and their ability to hover for surveillance missions. However, undesirable aerodynamic characteristics are associated with these vehicles in crosswinds, namely momentum drag and asymmetric duct lift.
Because the duct itself, and not the fan, is the root cause of these unfavorable aerodynamic attributes, various lip shapes were tested to determine the effects of leading edge radius of curvature and duct wall thickness. It was found that a lip with a small leading edge radius performed best in forward flight and crosswind conditions, while the performance of a lip with a large leading edge radius was enhanced in static conditions. Through tuft flow visualization and static pressure measurements it was determined that the reason for the difference in performance between the two lips was due to flow separation on the interior of the duct lip surface.
Control vanes positioned aft of the duct were tested as the primary attitude control for the vehicle. An empirical control vane model was created based on the static data for the control vanes, and it was applied to wind tunnel test results to determine the required control vane angle for trim. Wind tunnel testing showed the control vanes were capable of trimming out the adverse pitching moment generated by the duct, but at some flight speeds large vane deflections were necessary. Additional control devices placed at the lip of the duct and stabilizer vanes positioned aft of the duct were tested to reduce the amount of control vane deflection required for trim. It was found that the duct deflector control effector had the largest impact on the adverse pitching moment, while the stabilizer vanes were only effective at low crosswind velocities.
Filename Size Approximate Download Time (Hours:Minutes:Seconds)
28.8 Modem 56K Modem ISDN (64 Kb) ISDN (128 Kb) Higher-speed Access WGraf_Thesis_2005.pdf 4.88 Mb 00:22:35 00:11:37 00:10:09 00:05:04 00:00:26
If you have questions or technical problems, please Contact DLA.