Accession Number:

ADA090756

Title:

Stability of Nonuniform Rotor Blades in Hover Using a Mixed Formulation,

Descriptive Note:

Corporate Author:

ARMY RESEARCH AND TECHNOLOGY LABS MOFFETT FIELD CA

Personal Author(s):

• Stephens,Wendell B.
• Hodges,Dewey H.
• Avila,John H.
• Kung,Ru-Mei

Report Date:

1980-01-01

Pagination or Media Count:

20.0

Abstract:

A mixed formulation for calculating static equilibrium and stability eigenvalues of nonuniform rotor blades in hover is presented. The static equilibrium equations are nonlinear and are solved by an accurate and efficient collocation method. The linearized perturbation equations are solved by a one-step, second-order integration scheme. The numerical results correlate very well with published results from a nearly identical stability analysis based on a displacement formulation. Slight differences in the results are traced to terms in the equations that relate moments to to derivatives of rotations. With the present ordering scheme, in which terms of the order of squares of rotations are neglected with respect to unity, it is not possible to achieve completely equivalent models based on mixed and displacement formulations. A study of the one-step methods reveals that a second-order Taylor expansion is necessary to achieve good convergence for nonuniform rotating blades. Numerical results for a hypothetical nonuniform blade, including the nonlinear static equilibrium solution, were obtained with no more effort or computer time than that required for a uniform blade with the present analysis. Author

Descriptors:

• *HELICOPTER ROTORS
• *ROTOR BLADES(ROTARY WINGS)
• *AERODYNAMIC LOADING
• COMPUTERIZED SIMULATION
• STABILITY
• TAYLORS SERIES
• MATRICES(MATHEMATICS)
• FINITE ELEMENT ANALYSIS
• EIGENVALUES
• BOUNDARY VALUE PROBLEMS
• CONVERGENCE
• TABLES(DATA)
• PERTURBATIONS
• INTEGRAL EQUATIONS
• HOVERING

Subject Categories:

• Helicopters
• Theoretical Mathematics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE