A nonlinear unsteady flexible wing theory

outstanding scholarship, and for paying a sincere tribute to his most distinguished life and work. Abstract. This paper extends a previous study by Wu (2001)[1] to continue developing a fully nonlinear theory for calculation of unsteady flow generated by a two-dimensional flexible lifting surface moving in arbitrary manner through an incompressible and inviscid fluid for modeling bird/insect flight and fish swim-ming. The original physical concept elucidated by Theodore von Kármán and William R. Sears (1938)[2] in describing the complete vortex system of a wing and its wake in non-uniform motion for their linear theory is adapted and applied to a fully nonlinear consideration. The new theory employs a joint Eulerian and Lagrangian description of the lifting-surface movement to facilitate the formulation. The present investiga-tion presents further analysis for addressing arbitrary variations in wing shape and trajectory to achieve a nonlinear integral equation akin to Herbert Wagner’s (1925)[3] linear version for accurate computation of the entire system of vorticity distribution. Key words: nonlinear unsteady flexible wing theory, unsteady camber function, arbitrary trajectory. 1