Figure 3.
Sample images of hummingbird wake at the end of the upstroke for the (i) parasagittal and (ii) transverse planes. (a) Start vortex (1) and stop vortex (2) of the downstroke; LEVD, the leading-edge vortex shed at the end of downstroke; LEV2, the leading-edge vortex of the next downstroke and the start vortex for the upstroke (3). LEV refers here to the secondary vorticity tentatively identified as a leading-edge vortex from the wing (see text for details). (b) Tip vortex (4) and root vortex (5) for the downstroke, tip circulation (6) and root circulation (7,8) for the upstroke. The silhouette of the bird is included for clarity. Colour bar indicates vorticity (s−1).