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Fig. 16. Lift coefficients as functions of time for a two-winged clap and fling
stroke. The letters i–viii along the x axis correspond to the
times the streamlined plots labelled i–viii in
Fig. 15A,C were drawn. The
angle of attack during pure translation was set to 45°. The Reynolds
number (Re) was varied by changing the translational velocity of the
wing from 0.00375 to 0.06 m s–1. In general, lift
coefficients were larger at higher Re during the initial upstroke.
Lift coefficients, however, were smaller at higher Re during fling
and subsequent translation. For Re=64 and higher, lift coefficients
peak during translational acceleration and rotation. Lift coefficients drop
when the leading edge vortices separate from the wings (vii–viii). For
Re=32 and below, lift coefficients also peak during translational
acceleration and rotation. Lift coefficients are relatively constant during
translation in the first half-stroke (i–iii). Lift coefficients are
transiently augmented during translation after fling (vi–viii).
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