Fig. 1. Sketches of the reference frames and wing motion. (A) OXYZ is an
inertial frame, with the XY plane in the stroke plane. oxyz
is a frame fixed on the wing, with the x axis along the wing chord,
and the y axis along the wing span.
is the azimuthal angle of
the wing,
is the angle of attack and R is the wing length.
(B) The motion of a section of the wing.