Fast Lifting Surface Models for Rotorcraft Analysis

Current comprehensive rotorcraft analyses typically use lifting line theories coupled with 2D look-up tables to determine rotor blade lift, drag and pitching moment. These methods cannot directly capture 3D flow effects that influence the aerodynamic characteristics of advanced planforms, complex tip-shapes and low aspect ratio wing/tail surfaces. CFD codes have been coupled to comprehensive codes to provide this capability, but these coupled solutions are too computationally expensive for daily design work. The Phase I effort demonstrated the potential of lifting surface blade models to partially bridge the gap between lifting line models and full CFD solutions without excessive increase in computation time. The lifting surface model developed in Phase I was shown to better predict lift, drag and pitching moment than lifting line models near the tip of the blade and where strong blade-vortex interactions occurred. The proposed Phase II effort would further enhance and accelerate this lifting surface blade model and then provide comprehensive documentation of its effectiveness in modeling fixed and rotating wings in both steady and unsteady flow. The new lifting surface blade model would then be implemented, demonstrated and delivered as a new option within the U.S. Army"s Rotorcraft Comprehensive Analysis System (RCAS).