A methodology for the finite-state linear description of unsteady aerodynamic loads acting on the main rotor, when the rotor-fuselage configuration is perturbed from its equilibrium condition, is presented. In fixed-wing aircraft aerodynamics, the finite-state coefficients are time independent. For helicopter rotors this is true only for the limited case of hovering conditions with state variables describing a motion normal to the rotor disk. Otherwise, the finite-state description coefficients are time dependent and, in particular, periodic. Here, we present a methodology for the reconstruction of aerodynamic finite-state coefficients for hovering rotors subject to perturbation motion both (i) normal to the rotor disk and (ii) in the plane of the rotor disk. It is based on a boundary-element solution of the aerodynamic field induced by the Lagrangean variables of interest (for instance, amplitude of structural vibration modes, displacements of the hub, angles of rotation of the rotor disk). Under the assumptions of incompressible, potential flows, in this work, frequency-domain aerodynamic loads are determined by a boundary-element formulation for the velocity potential, coupled with the Bernoulli theorem. Numerical results for the validation of hovering rotor finite-state approximation of aerodynamic loads arising from in-plane and out-of-plane disturbances are included.
Periodic-coefficient finite-state aerodynamic modelling for rotor dynamics of helicopter configurations
Aerodynamische Modellierung mit endlichen, periodischen Koeffizienten für die Rotordynamik von Hubschrauberkonfigurationen
1997
9 Seiten, 9 Bilder, 16 Quellen
Conference paper
English
British Library Conference Proceedings | 1997
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