Nonlinear aeroelastic analysis of control surface with freeplay using computational-fluid-dynamics-based reduced-order models

A computational-fluid-dynamics-based aeroelastic analysis method is proposed to simulate control-surface limitcycle oscillation (LCO) induced by freeplay gap. The present method is based on the previously proposed aeroelastic reduced-order model (ROM), in which an unsteady aerodynamic state-space model is generated from aerodynamic responses to step excitation of individual mode using the eigensystem realization algorithm, and connected to a structural dynamic state-space model within the MATLAB/SIMULINK environment. The aeroelastic ROM is extended to treat structural nonlinearity due to the control-surface freeplay by generating an additional feedback line of generalized residual forces in the SIMULINK model. To reduce the problem size and the computation time, a fictitious-mass modal approach is used, which can afford the possible local change of stiffness. The present method is first validated for its capability to simulate aeroelastic responses of a regional-jet horizontal-tail (HT) model without freeplay, and shows good prediction of flutter characteristics measured in the transonic flutter wind-tunnel testing. The present method is then applied to the HT model with the elevator freeplay gaps. Although there are some differences between the computed and measured limit-cycle-oscillation ranges, the present method well predicts the nonlinear limit-cycle-oscillation behavior in its amplitude and frequency measured in the test, and shows promise toward accurate prediction of control-surface LCO due to its freeplay gap. Copyright