Steady flow analysis of a slender wing by lifting surface method

In the paper hereby, steady flow around a thin-walled wing is analysed by means of the Lifting Surface Method. In order to carry out tests, the wing has been divided into a finite number of quadrilateral panels. All panel edges in turn are replaced by discrete straight vortex segments which induce velocities within the flow field. The problem boils down to working out velocity circulation distribution on the wing surface. For this purpose, numerical realization has been developed in C by Minimalist GNU for Windows compiler and Code::Blocks IDE. To work out a solution to the linear non-homogeneous algebraic system, the Gauss – Seidel stationary iterative method has been applied. The obtained results for various angle of attack values are depicted by means of ParaView.

Nonlinear Responses of a Slender Wing With a Store

The aeroelastic characteristics of the slender wing with store have been studied for several years. However, the nonlinear aeroelastic behaviors of the wing-store system have not been understood thoroughly. In this paper, the nonlinear aeroelastic model of a slender wing with a store is constructed. In the model, the geometric structural nonlinearity of the wing, and the kinematic nonlinearities of the wing and the store are considered. Two unsteady aerodynamic models are both employed to determine the aerodynamic loads. One is the linear unsteady aerodynamic model based on Wagner function, and the other is the nonlinear ONERA aerodynamic model. Simulation results are given to show that for the cases of employing the linear unsteady aerodynamic model based on Wagner function, the bifurcation diagrams are very complex and change with the variations of store position. For the cases of using the nonlinear ONERA model, the bifurcation diagrams are very simple and insensitive to the variations of the store position. Additionally, with the decrease of store spanwise coordinate, the system bending oscillation equilibrium position is reduced to zero, and the maximum absolute value of the bending response peak is also decreased. With the increase of the horizontal distance between the wing elastic center and the store mass center, the system response peak is decreased. Moreover, it is found that for the systems with the linear unsteady aerodynamic model based on Wagner function, the obtained response peak is larger and the nonlinear critical velocity is smaller than those with the ONERA model.

Effects of Externally Mounted Store on the Nonlinear Response of Slender Wings

The nonlinear characteristics of slender wings have been studied for many years, and the influences of the geometric structural nonlinearity on the postflutter responses of the wing have been received significant attention. In this paper, the effects of the external store on the nonlinear responses of the slender wing will be discussed. Based on the Hodges–Dowell beam model, the dynamical equations of the wing which include the geometric structural nonlinearity and store effects are constructed. The unsteady aerodynamic loading of the wing will be calculated by employing Wagner function and strip theory. The slender body theory is adopted to get the aerodynamic forces of the store. The Galerkin method is used to obtain the state equations of the system and the appropriate mode combination is obtained for the cases studied in this paper. Numerical simulations are given to show that the store spanwise position and the distance between the store mass center and the elastic center of the wing are two important factors which will affect the nonlinear characteristics of the wing. These two parameters will induce the occurrence of quasi-periodic motion and branch structure in bifurcation diagrams to the system. The peak of postflutter response is also related to these parameters and the lower response peak can be obtained when the store mass center is in front of the elastic center. The models and results are helpful to the design procedure of the slender wing with store in the preliminary stage.