ROTOR WAKE MODELING FOR HIGH SPEED APPLICATIONS.
The effect of various wake models on the prediction of rotor vibratory airloading has been studied in an ongoing research program on wake aerodynamics in high speed flight. At high advance ratios, the rotor wake structure is particularly complicated and the simple tip vortex representation often used in the past is inadequate. On the advancing side the generating blade may experience large spanwise and azimuthal load variations, including negative tip loading. New analysis methods have been developed to represent the important features of high speed wakes. One approach involves multiple filament kinematic wake models. The necessary features of such models and the flight conditions under which they perform reasonably well are discussed. The development of a novel multi-filament, full span free wake analysis using curved vortex elements is also described. The curved filaments are laid down along contours of constant vortex sheet strength thereby providing a natural representation of the wake that automatically accounts for both trailed and shed vorticity components.
