Leading-edge vortices over swept-back wings with varying sweep geometries

• Published in: Royal Society Open Science
• Main Authors: William B. Lambert, Mathew J. Stanek, Roi Gurka, Erin E. Hackett
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 2019
• Subjects: leading-edge vortex; swift; delta; swept-back wings; particle image velocimetry; Science; Q; Apus apus
• Online Access: https://doi.org/10.1098/rsos.190514; https://doaj.org/article/73a0c4126b2c4835b3c5385d159477b0

Micro air vehicles are used in a myriad of applications, such as transportation and surveying. Their performance can be improved through the study of wing designs and lift generation techniques including leading-edge vortices (LEVs). Observation of natural fliers, e.g. birds and bats, has shown that LEVs are a major contributor to lift during flapping flight, and the common swift (Apus apus) has been observed to generate LEVs during gliding flight. We hypothesize that nonlinear swept-back wings generate a vortex in the leading-edge region, which can augment the lift in a similar manner to linear swept-back wings (i.e. delta wing) during gliding flight. Particle image velocimetry experiments were performed in a water flume to compare flow over two wing geometries: one with a nonlinear sweep (swift-like wing) and one with a linear sweep (delta wing). Experiments were performed at three spanwise planes and three angles of attack at a chord-based Reynolds number of 26 000. Streamlines, vorticity, swirling strength, and Q-criterion were used to identify LEVs. The results show similar LEV characteristics for delta and swift-like wing geometries. These similarities suggest that sweep geometries other than a linear sweep (i.e. delta wing) are capable of creating LEVs during gliding flight.