An Investigation of Bounding Flight for UAVs Kenneth
An Investigation of Bounding Flight for UAVs Kenneth Toro Advisor: Dr. Lance Traub Embry Riddle Aeronautical University of Arizona April 2010 1
Bounding Flight of Birds � Bounding is an intermittent retraction of wings. � Exclusive to small birds (less than 260 grams) � Theories for bounding flight: Fixed Gate/Gear � Reduction of power required � Figure: Bounding Flight of Birds (Source: Tobalake, 1999) 2
Wind Tunnel Model Table: Test Article Parameters Parameter 3 Value Span (in. ) 24. 1 Planform Area (in 2) 60. 0 Reference Chord (in. ) 2. 33 Aspect Ratio 9. 62 � Wind Tunnel Test were conducted at Reynolds number of 150, 000 and 85, 000 (45 m/s and 25 m/s). � A 32 in. by 45 in. closed circuit wind tunnel was used. � A 6 -component pyramidal balance was used to measure force data.
Wind Tunnel Results Minimum Drag vs. Sweep Angle Efficiency vs. Sweep Angle 0. 50 0. 09 0. 45 0. 08 0. 40 0. 07 0. 06 0. 30 CDmin Efficiency (e) 0. 35 0. 20 0. 04 0. 03 0. 15 0. 02 0. 10 Re 150 k 0. 05 Re 85 k 0. 00 0 4 0. 05 20 Sweep Angle (deg. ) Re 150 k 0. 01 Re 85 k 0. 00 40 0 20 Sweep Angle (deg. ) 40
Power Required vs. Flight Velocity 250. 0 Power Required (W) 200. 0 150. 0 100. 0 S 00 S 20 S 40 50. 0 0 5 10 20 30 Velocity (m/s) 40 50 60
Bounding Simulation Flight Path Wings Retracted Desired Alt. Wing Extended Figure: Desired Flight Bounding Flight Path � Thrust � Angle is the only variable. of Attack assumed to be constant. � Weight � Initial 6 is assumed to be 0. 7 kg. velocity was 25 m/s.
Bounding Simulation Results � Higher thrust while wings are extended leads to increase in the amplitude of oscillation. � Higher thrust while wings are retracted leads to an increase in energy used. � Bounding had a higher use of energy than steady level flight. 7
Conclusion and Recommendations � No performance improvement was achieve by bounding flight. � Power required at high speeds can be reduced by high wing sweep. � High � 8 wing sweep can improve gust alleviation. A redesign of the fuselage can reduce the body drag of the model.
Questions? Drago-B 9
- Slides: 9