Alula-inspired leading edge device for low Reynolds number flight

Boris A. Mandadzhiev, Michael K. Lynch, Leonardo P. Chamorro, Aimy A. Wissa

Research output: Chapter in Book/Report/Conference proceedingConference contribution

11 Scopus citations


Robust and predictable aerodynamic performance of unmanned aerial vehicles at the limits of their design envelope is critical for safety and mission adaptability. In order for a fixed wing aircraft to maintain the lift necessary for sustained flight at very low speeds and large angles of attack (AoA), the wing shape has to change. This is often achieved by using deployable aerodynamic surfaces, such as flaps or slats, from the wing leading or trailing edges. In nature, one such device is a feathered structure on birds' wings called the alula. The span of the alula is 5% to 20% of the wing and is attached to the first digit of the wing. The goal of the current study is to understand the aerodynamic effects of the alula on wing performance. A series of wind tunnel experiments are performed to quantify the effect of various alula deployment parameters on the aerodynamic per- formance of a cambered airfoil (S1223). A full wind tunnel span wing, with a single alula located at the wing mid-span is tested under uniform low-turbulence flow at three Reynolds numbers, Re = 85,000, 106,00 and 146,000. An experimental matrix is developed to find the range of effectiveness of an alula-type device. The alula relative angle of attack measured measured from the mean chord of the airfoil is varied to modulate tip-vortex strength, while the alula deflection is varied to modulate the distance of the tip vortex to the wing surface. Lift and drag forces were measured using a six axis force transducer. The lift and drag coefficients showed the greatest sensitivity to the the alula relative angle of attack, increasing the normalized lift coefficient by as much as 80%. Improvements in lift are strongly correlated to higher alula angle, with β = 0° - 5°, while reduction in the drag coefficient is observed with higher alula tip deflection ratios and lower β angles. Results show that, as the wing angle of attack and Reynolds number are increased, the overall lift coefficient improvement is diminished while the reduction in drag coefficient is higher.

Original languageEnglish (US)
Title of host publicationModeling, Simulation and Control; Bio-Inspired Smart Materials and Systems; Energy Harvesting
PublisherAmerican Society of Mechanical Engineers
ISBN (Electronic)9780791850497
StatePublished - 2016
Externally publishedYes
EventASME 2016 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS 2016 - Stowe, United States
Duration: Sep 28 2016Sep 30 2016

Publication series

NameASME 2016 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS 2016


ConferenceASME 2016 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS 2016
Country/TerritoryUnited States

All Science Journal Classification (ASJC) codes

  • Building and Construction
  • Civil and Structural Engineering
  • Control and Systems Engineering
  • Mechanics of Materials


Dive into the research topics of 'Alula-inspired leading edge device for low Reynolds number flight'. Together they form a unique fingerprint.

Cite this