GUST RESPONSE FOR FLAT-PLATE AIRFOILS AND THE KUTTA CONDITION

The case of a flat plate airfoil encountering a gust in incompressible flow is analyzed, with the generalization that the shed vorticity in the wake as well as the incident gust can convect at arbitrary velocity relative to the frees (ream. Bound vorticity and loading are calculated. At high frequency the bound vorticity is shown to be equivalent to an image of the incident gust, and drifts with the gust, except near the leading edge, and if the gust velocity is unequal to the wake velocity, near the trailing edge. When the wake moves relative to the freestream, there is a loading on the wake which forces nonzero loading at the trailing edge. A recent vortex chopping model is shown to depend explicitly on this fictitious wake loading, raising questions about the resulting noise prediction. A clarification in the application of the Kutta condition is given for the case of high frequency gust disturbances when both the gust and the wake drift with the freestream, showing that for inviscid flow the Kutta condition is satisfied automatically as the gust passes the trailing edge by allowing the flow to continue as if the edge were not present. © 1990 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.