Click on image to view larger version.

Fig. 1. Cross section of an airfoil illustrating geometry of the principal model
parameters. (A) The arrows indicate that the wing is translating to the left
due to root-flapping and rotating about the point r due to active
supination or pronation. Point i is the location of the incident
flow, which is illustrated in (B). The subscript (r) has been removed from
r,
i and c for clarity. (B)
The relevant flow velocity components due to root-flapping
and wing rotation
and their resultant,
(r,t). Also illustrated are the wing
pitch,
, the geometric attack angle,
g, and the angle
of incidence,
', acting at the point i in (A).