Fig. 17. LEV formation and growth on a flat plate plunging harmonically at 13 Hz in a 2.0 m s^–1 flow (mean angle of attack 15°; 8 ms frame separation). Plunging is presented here because the plate never obscures the view – the flow field is similar in flapping or pitching motions (Taylor et al., 2003). (A–F) Detailed features of the flow topology over dragonfly forewings are reproduced with kinematics configured for , as in real dragonflies. No starting vortex is produced: instead a vortex sheet forms in the shear layer behind the trailing edge (B–F), and transverse vortices of circulation opposite to the circulation of the LEV roll up under Kelvin–Helmholtz instability (C–G). The LEV grows through the downstroke (B–E) and translates back across the wing chord at the end of the downstroke (F). The LEV is eventually shed into the wake on the upstroke (G–J). Video S3 in supplementary material is an animation of this sequence including three additional intervening frames between every frame included in the figure.