The Influence of a Nonzero Angle of Attack and Gust Loads on the Nonlinear Response of a Typical Airfoil Section with a Control Surface Freeplay

Abstract

The influence of a "frozen" harmonic gust excitation on an aeroelastic nonlinear system with a control surface freeplay at nonzero angles of attack is examined in the context of a three-degree-of-freedom airfoil. The formulation of the numerical model is based on Theodorsen's aerodynamics and is extended to account for nonlinear arbitrary motion and gust loads. By time marching of the governing equations, the system response is determined and the complex nonlinear behavior is observed. Results indicate that there is no suppressing effect due to a nonzero mean angle of attack for such a system under gust loads. A companion experimental test program in a wind tunnel with a gust generator is used to validate the numerical results. The good agreement between theory and experiment demonstrates the efficiency and accuracy of the computational method.

Performance Improvement of Small Unmanned Aerial Vehicles Through Gust Energy Harvesting

“…Those functions are also available for several aspect ratios, which enables comparison for various wing dimensions. The complete system of equations for a nonlinear response of a typical airfoil section exposed in the state-space formulation was done by Kholodar and Dowell [34].…”

Worst-Case Gust-Response Analysis for Typical Airfoil Section with Control Surface

“…(19)(20)(21), C(k) is the Theodorsen's function and k = bω/U is the reduced frequency. The downwash at the 75% chord is given by…”

“…The R. T. Jones approximation 19 to the Wagner function is often used for a gust study 20,21 and is also used in this paper,…”

“…(18) to the Laplace domain, and substituting Laplace transformed Eqs. (19)(20)(21)(22), (25), (26), (28), and (29-34) with the initial condition equation (38). In the matrix form, the equation is given by…”

Local Stabilization of a Fluid--Structure System around a Stationary State with a Structure Given by a Finite Number of Parameters

“…More precisely, the structure is a smooth approximation of a steering gear depending on two angles of deformation θ 1 and θ 2 . Such a kind of structure can be found for instance in aeronautics [18]. Our goal is to design a finite dimensional feedback controller which stabilizes locally the system around a given stationary state at any prescribed exponential decay rate.…”