Free wake flow field calculations for rotorcraft interactional aerodynamics

The principal objective of this work was to explore the applicability of recent innovations in the analysis of vortex dynamics to problems of interest in rotorcraft interactional aerodynamics. Using a novel, full-span rotor wake representation constructed of curved vortex elements, accurate qualitative and quantitative predictions of wake velocity data were achieved for rotors in both low- and high-speed forward flight. The flowfield predictions also illustrated the radical changes that take place in the wake velocity field as speed increases and demonstrated the success of this new approach in capturing these variations. In addition, new methods for analyzing close interactions between vortices an fixed surfaces have been developed. The basis of this new approach is the inclusion of a special treatment of the vortex velocity field for close interactions with paneled surfaces which obviates the need for high local panel density. Model problems were solved featuring vortices in close proximity to surfaces that illustrate the accuracy and efficiency of the new method. The results of this effort indicate that the new analysis techniques described here are a suitable foundation for a general analysis of interactional aerodynamics.