3

Aerodynamic Considerations

27

Fig. 3.2 Stall in an insect and aeroplane (Modified and redrawn from various sources)

leading edge vortex at high angles of attack. This in turn helps the insect to generate

additional force by the wing and helps to hover. During upstroke, the wing is pushed

upward and backward followed by a pronation (upstroke to downstroke) so as to

allow another downstroke (Fig. 3.3). The term wing rotation during these two types

of strokes refers to the changes in the angle of attack around a chordwise axis. Hence,

the calculations of aerodynamic forces during an insect flight appear to depend on

the theories based on wing rotation in different insect species.

Fig. 3.3 Forces acting on a

flapping wing during

downstroke and upstroke