Results show that, in general, the location of the LEAD root yielding the highest lift enhancement was 50% semi-span away from the wing root. To quantify the aerodynamic effect of the device, the lift generated by the wing with and without the LEAD were measured using a 6-axis force and torque transducer, and the resulting lift coefficients were compared. Wind tunnel experiments were conducted on a wing with an S1223 airfoil at post-stall and deep-stall angles of attack and at low Reynolds numbers of 100,000 and 135,000. This research presents the effect on lift generation of different placements of the LEAD along the span of a moderate aspect-ratio wing.
For finite wings, on the other hand, the effect depends on the interaction between the LEAD’s tip vortices and those from the main structure. The effect of the LEAD can be compared to traditional slats or vortex generators on two-dimensional wings. It also generates tip vortices that modify the turbulence on the upper-surface of the wing, delaying flow separation. The proposed alula-inspired leading-edge device (LEAD) increases the capability of a wing to maintain higher pressure gradients by modifying the near-wall flow close to the leading-edge. Equipped with a set of small feathers, known as Alula, located near the leading edge and covering 5% to 20% of the span, bird wings can sustain the lift necessary to fly at low velocities and high angles of attack. Birds mitigate those limitations by adapting their wings and feather shapes during flight. Degree Level Thesis Keyword(s)Ībstract Even though Unmanned Aerial Vehicles (UAVs) operating at low Reynolds numbers are becoming common, their performance and maneuverability are still greatly limited due to aerodynamic phenomena such as stall and flow separation.
Issue Date Director of Research (if dissertation) or Advisor (if thesis) Wissa, Aimy A Department of Study Mechanical Sci & Engineering Discipline Mechanical Engineering Degree Granting Institution University of Illinois at Urbana-Champaign Degree Name M.S. I’ve circled one of Dorothy’s in red so you know what to look for, or check yesterday’s blog and you’ll see both alulas on the great egret, raised like thumbs pointing to the sky.Title An experimental study of a leading-edge alula-inspired device (LEAD) for moderate aspect ratio wings at low Reynolds numbers Author(s) Ito, Mihary R. So when you see a bird landing or attacking, look for its alulas. Look out the window of a jet before take-off and you’ll see the slats have been moved away from the leading edge of the wing. Wikipedia explains that this allows “a higher than normal angle of attack” which is exactly what Dorothy (the adult female peregrine at Pitt) is doing here - attacking the bird banders who are coming for her babies.īig airplanes solve the same problem of creating lift with movable parts called slats that act like alulas. In this position the air can flow faster over the top of the wing, creating lift when the wing is perpendicular to the ground. Normally it lays flat on the wing and is hard to see but birds raise their alulas to prevent a stall during slow flight.
The alula is the bird’s “thumb” positioned on the top edge of the wing and covered with three to five small feathers depending on the species. This is my favorite part of bird anatomy because I see peregrine falcons use it to such good advantage.
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