Numerical convergence, stability, and accuracy characteristics of the methodology are discussed in detail in the available publications. The pseudo- implicit numerical scheme is compared with more conventional explicit-type free-wake algorithms such as those currently used in CAMRAD and 2GCHAS to demonstrate the enhanced stability and convergence trends of the new scheme. The method is shown to approach a grid-independent wake solution for increasing discretization resolutions, and converges to a unique solution. The use of typical artificial tuning parameters, such as adjustable core radii, has also been eliminated from the formulation, resulting in a scheme that is significantly more robust and versatile than existing methods. The method is also extended to investigate the flow field structures of tandem, side-by-side and coaxial rotor configurations.
The method has been applied to examine rotor wake geometries for a wide variety of geometric rotor configurations and flight conditions, including variations in advance ratio, rotor thrust, number of blades and rotor shaft angles. Comparisons between predictions and experiment are made in the published papers for wake geometries, wake boundaries, rotor induced inflow distributions and flow field velocities, to help validate the predictive capabilities of the new method. The overall agreement between the predictions and experiment are demonstrated to be good.
Predicted wake geometry for a 4-bladed rotor at several advance ratios
Bagai, A., Leishman, J.G., "Free-Wake Analysis of Tandem, Tilt-Rotor and Coaxial Rotor Configurations," Presented at the 51st Annual Forum of the American Helicopter Society, Fort Worth, TX, May 9-11, 1995.
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