Fig. 3. Circulation along the wing span. (A) Circulation as a function of non-dimensional spanwise position for the case example of a Drosophila wing. The red curve shows the functional form of chord length as a function of non-dimensional spanwise position, and the green curve shows the functional form of circulation for a revolving propellor blade with a varying lift coefficient that varies linearly from base to tip. The black curve depicts the final functional form of the circulation on an insect wind obtained by multiplying the values generating the red and blue curves. (B). Comparison of the theoretically derived circulation variation with an experimentally derived distribution of circulation from DPIV data in a model Drosophila wing from Birch et al. (2004).