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A variational approach to multipoint aerodynamic optimization of conventional and coaxial helicopter rotors

Publication ,  Conference
Giovanetti, EB; Hall, KC
Published in: Annual Forum Proceedings - AHS International
May 2015

© 2015 by the American Helicopter Society International, Inc. We present a variational approach to the multipoint aerodynamic design optimization of conventional and coaxial helicopter rotors. The optimal design problem is cast as a variational statement that minimizes the weighted sum of induced and viscous power losses between two flight conditions for prescribed vehicle trim constraints at each flight condition. The resulting nonlinear constrained optimization problem is solved via Newton iteration and may be used to map the Pareto frontier, i.e., the set of rotor designs (radial twist and chord distributions and harmonic blade pilch inputs) for which it is not possible to improve upon the performance in one flight conditions without degrading performance in the other. The two flight conditions can represent different advance ratios (including hover), disk loadings, altitude, or other conditions of interest. For forward flight computations, the rotor control inputs arc related to the circulation on the blades (and in the wake) through a lifting-line/vortex-lattice method that accounts for nonlinear sectional lift and drag polars. For hovering flight, the rotor performance is analyzed using Blade Element Momentum Theory. We map the Pareto frontier for both a cruise/cruise and hover/cruise multipoint optimization, and show that significant tradeoffs must be made in designing a rotor to balance performance between two flight conditions, particularly hover and high speed forward flight. We also show that higher harmonic control is capable of reducing rotor power and improving the Pareto frontier, particularly for coaxial rotors. Finally, we present a number of rotor designs that best balance performance between two flight conditions.

Duke Scholars

Published In

Annual Forum Proceedings - AHS International

ISSN

1552-2938

Publication Date

May 2015

Volume

2

Issue

May

Start / End Page

752 / 764
 

Citation

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MLA
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Giovanetti, E. B., & Hall, K. C. (2015). A variational approach to multipoint aerodynamic optimization of conventional and coaxial helicopter rotors. In Annual Forum Proceedings - AHS International (Vol. 2, pp. 752–764).
Giovanetti, E. B., and K. C. Hall. “A variational approach to multipoint aerodynamic optimization of conventional and coaxial helicopter rotors.” In Annual Forum Proceedings - AHS International, 2:752–64, 2015.
Giovanetti EB, Hall KC. A variational approach to multipoint aerodynamic optimization of conventional and coaxial helicopter rotors. In: Annual Forum Proceedings - AHS International. 2015. p. 752–64.
Giovanetti, E. B., and K. C. Hall. “A variational approach to multipoint aerodynamic optimization of conventional and coaxial helicopter rotors.” Annual Forum Proceedings - AHS International, vol. 2, no. May, 2015, pp. 752–64.
Giovanetti EB, Hall KC. A variational approach to multipoint aerodynamic optimization of conventional and coaxial helicopter rotors. Annual Forum Proceedings - AHS International. 2015. p. 752–764.

Published In

Annual Forum Proceedings - AHS International

ISSN

1552-2938

Publication Date

May 2015

Volume

2

Issue

May

Start / End Page

752 / 764