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A State‐Space Airloads Theory for Flexible Airfoils

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In this paper, classical thin airfoil theory is extended in four ways. First, the theory is reformulated to apply to an airfoil that is performing large frame motions with respect to the air mass. Second, airfoil motions within the frame are allowed to include completely general dynamic deformations of the cross‐section. Third, the theory is formulated in terms of generalized deflections and generalized forces within that frame, which leads to mass, damping, and stiffness matrices for the generalized airfoil motion. Fourth, although most of the applications herein are in the context of a two‐dimensional flat wake in the frequency domain (as in Theodorsen theory), the theory is cast such that it can be coupled with any unsteady wake model desired, including three‐dimensional wake models such as vortex‐lattice. Comparisons with other theories will show that this new theory includes the classical theories of Wagner, Theodorsen, Garrick, Loewy, Greenberg, and Isaacs when applied to those special cases.

Document Type: Research Article


Affiliations: Department of Mechanical and Aerospace Engineering, Washington University, Campus Box 1185, St. Louis, MO

Publication date: October 1, 2007

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  • The Journal of the American Helicopter Society is the world's only scientific journal dedicated to vertical flight technology. It is a peer-reviewed technical journal published quarterly by AHS International and presents innovative papers covering the state-of-the-art in all disciplines of rotorcraft design, research and development. (Please note that AHS members receive significant discounts on articles and subscriptions.)

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