Aeroelastic Stability of Composite Hingeless Rotors in Hover with Finite‐State Unsteady Aerodynamics
Abstract:An approach to hovering rotor aeroelasticity analysis is presented which integrates geometrically‐exact nonlinear beam theory and the generalized dynamic wake theory within a finite element basis, forming a precise and compact formulation. In the development, all the advantageous features of the geometrically‐exact beam theory are retained. In the finite element discretization, the simplest possible shape functions are used in conjunction with the weakest form of the equations, thus avoiding numerical quadrature and yielding very sparse system matrices. When integrating the structure and lifting models with the finite‐state inflow formulation, the lifting surface is consistently discretized so that numerical calculations for structural and aerodynamic fields are carried out to the same degree of accuracy. The final aeroelastic system is presented in an operator form that has concrete physical meaning and compact mathematical expressions. This formulation has the following features: (1) geometrical exactness in the one‐dimensional beam analysis; (2) ability to model composite blades with the use of asymptotically exact cross‐sectional analysis; (3) three‐dimensional unsteady aerodynamics; (4) ability to model complicated configurations, including pretwist, initial curvature, and advanced tip geometry; (5) compact form; and (6) high computational efficiency. The formulation's performance is demonstrated through numerical examples and presents aeroelastic stability analysis results for rotor blades with advanced geometries, including initially curved and twisted composite blades and composite blades with tip sweep, anhedral and dihedral. Results show that composite blades with appropriately chosen values of initial twist and curvature can exhibit significantly improved stability characteristics while simultaneously reducing steady‐state loads.
Document Type: Research Article
Affiliations: School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, Georgia
Publication date: 1999-07-01
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