The Unsteady Motion of Slender Wings with Leading-Edge Vortices

The unsteady motion of thin, slender wings with leading-edge vortioes is considered. Incompressible flow and slender-wing theory are assumed throughout , and use is made of an analogy between the unsteady flow and related steady flows. The particular motions treated are: (i) a sudden plunging motion, or change of incidence, (ii) entry into a gust, For the first case, it is shown that the flow in any transverse plane moving with the wing reaches its steady state as scan as that plane has travelled past the initial position of the leading apex of the wing. An extension of the theory of Brown and Michael is given to determine the strength of the vortex and its path from the leading-edge to the steady-state position, Preliminary results obtained are compared with experiment, For the second case, use of the analogy shows that quasi-steady theory holds, The flow in any transverse plane is instantaneously in the steady state corresponding to the effective incidence produced there by the gust.