| High-alitude long-range UAV is a trend for future development,it raises the concern of many researchers.However,the lightweight composite wings of such aircraft produce large deformation,which leads to significant structural geometric noninearity.So that the coupling between the aerodynamic load and the elastic structural response becomes more and more serious,and there is a strong possibility of strong instability such as airfoil divergence and flutter.So the conventional aeroelastic analysis method based on the linear theory is not suitable for such a large deformation of the nonlinear structure.Therefore,it is necessary to carry out the study of geometric nonlinear modeling technique and subsequent nonlinear aeroelastic analysis method for composite wing with high aspect ratio.At the same time,taking into account the irrational wing stiffness design will lead to reverse divergence and flutter and other aeroelastic problems,it is necessary to carry out the study of stiffness characteristics and its influence on static aeroelastic and flutter for composite wing with high aspect ratio.The main research contents and innovations are as follows:1.A more efficient method of structural geometric nonlinear modeling is developed.An efficient linear 4-node thin shell element is established in the local coordinate system,and a nonlinear 4-node thin shell element is established by introducing a method named ‘Co-rotational' considering large displacement and small strain of structure.A number of examples verify the effectiveness of the nonlinear analysis method,which provides modeling support for subsequent aeroleastic analysis of composite wings with high aspect ratio.2.The nonlinear static aeroelastic analysis method of the wing with high aspect ratio is studied.the structural analysis is carried out by using the structural geometric nonlinear analysis method,and the information transfer of the wing coupling surface is realized by dynamic grid technology.The applicability of the method is verified by a model wing with high aspect ratio.Finally,the influence of the geometrical nonlinearity caused by the large deformation of the wing on the pressure distribution of the coupling surface and the bending and torsional deformation of the wing structure is studied.3.An effective method for solving the three-dimensional flutter problem is proposed.Flutter analysis is carried out considering structural geometric noninearity for composite wing with high aspect ratio.Load and deformation transfer and dynamic mesh method were used to transfer the nodal load and deformation of fluid-structure interface.The experimental data of the international standard flutter experiment with AGARD 445.6 wing is introduced to verify calculation accuracy of the flutter analysis method and program,which is applied to the flutter analysis of a composite wing with high aspect ratio of a certain type.4.Taking into account the unreasonable rigidity of the composite wing with high aspect ratio will lead to instability of static aeroelastic and flutter and other aeroelastic problems.Based on thin-walled structure mechanics,the impact analysis of geometric parameters and layouts of beam and stringer on the stiffness and stiffness center are then accomplished.In order to discuss the impact of beam and stringer on stiffness,sensitivity formulas for stiffness center are established according to the dimension and layout of them.5.The influence of stiffness on the aeroelastic of composite wing with high aspect ratio is studied.The nonlinear static aeroelastic and flutter calculations are carried out for two wing with different stiffness distributions,the purpose is to study the impact of stiffness on aeroelastic by comparing the calculation results of static aeroelastic deformation,pressure distribution,lift,lift-drag ratio and flutter critical velocity,respectively.The degree of influence of stiffness on the aeroelastic is determined.To achieve the integrated design such a wing on aeroelastic and stiffness. |
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