A finite‐slate wake model is used to investigate aeromechanical stability of hingeless‐rotor helicopters in the ground‐contact, hover and trimmed‐flight conditions. The investigation covers three items: (1) the convergence of the damping with increasing number
of wake harmonics for the lag regressing, and body pitch and roll modes; (2) a parametric study of the damping over a range of thrust level, advance ratio and number of blades; and (3) correlations, primarily with the damping and frequency measurements of these lag and body modes. The convergence
and parametric studies are conducted in the hover and trimmed‐ flight conditions; they include predictions from the widely used dynamic inflow model. The correlations are conducted in the ground‐contact conditions and include predictions from the dynamic inflow and vortex models;
recently, this vortex model is proposed for the axial‐flight conditions and is used to investigate the coupled free vibrations of rotor flapping and body modes. The convergence and parametric studies show that a finite‐state wake model that goes well beyond the dynamic inflorv
model is required for fairly converged damping. Moreover, the correlations from the finite‐state wake, dynanuc inflow and vortex models are generally satisfactory.
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Document Type: Research Article
Department of Aerospace Engineering, Indian Institute of Science, Bangalore, India
Publication date: 1999-07-01
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