Aeroelastic study for folding wing during the morphing process

This paper focuses on the aeroelastic characteristics of a folding wing during the morphing process. The folding wing structure is modeled by using the flexible multi-body dynamics approach, and an efficient method is proposed to calculate the aerodynamic force of the folding wing during the morphing process. The aerodynamic influence coefficient (AIC) matrices at different folding angles are obtained by the Doublet Lattice based aerodynamics theory, and then the orders of these AIC matrices are reduced by the spline interpolation technique. Through the minimum state approximation, the reduced AIC matrices are described as rational functions in the Laplace domain. Then the Kriging agent model technique is used to interpolate the coefficient matrices of the rational functions obtained from several different folding angles and to build the aerodynamics model in the time domain. At some different folding angles, the element values of the coefficient matrices before and after the interpolation are compared to verify the accuracy of the aerodynamics model, and then the aeroelastic responses of the folding wing during its morphing processes are simulated. The results demonstrate that the folding and unfolding processes have opposite influences on the dynamic aeroelastic stability of the folding wing, and the influences become much more significant with the increasing of the folding and unfolding rates. When the folding wing is morphing with a very slow rate, the dynamic aeroelastic stability will be similar to that obtained by the quasi-steady aeroelastic analysis.