A Computational Study of Trailing-Edge Flap Aerodynamics and Acoustics

An Euler solver is used to obtain indicia! responses from trailing-edge flaps and pitching airfoils in subsonic flow. Lift and moment time histories on the airfoil are obtained using several approaches and compared with approximate analytical solutions from indicia! method. The active control of blade vortex interaction (BVI) noise by a trailing-edge flap or airfoil pitching motion is examined. The motion required to minimize the BVI loading are obtained by a recursive formulation based on indicial concepts, and the minimization is validated by CFD calculations. Such CFD calculations give quite accurate results and are useful to validate and derive CFD optimized analytical approximations in the absence of experimental data. Furthermore, unsteady chordwise pressure distributions and resulting flow-field pressure disturbance contours are available to understand the effects of incorporating active control surfaces to minimize the unsteady lift. The pressure time histories at typical locations, as well as contour plots of overall sound pressure levels provide further insight into the physical noise generation mechanisms for active control. The actuation rates and non-compactness of source noise mechanisms are investigated to determine feasibility for both strong and weaker interactions.