Analysis Of Nonlinear Aeroelastic Of High Aspect Ratio Wings

The high-altitude, long-endurance unmanned air vehicles (UAV) have widely applications andbecome the research focus in aeroelastic community. The characteristics of geometric nonlinearity aresignificant due to its high-aspect-ratio wing. Nonlinear aeroelastic analysis becomes the key techniquefor designing these kinds of air vehicles. In this thesis, the problems of nonlinear aeroelastic responsesof high-aspect-ratio wings were studied profoundly.1、Firstly, a structural solver for computation of nonlinear dynamic response was established. Ahigh accuracy quadrilateral flat-shell element with rotational degrees of freedom is presented. Thiselement has the capability to eliminate the shear locking problem by assuming reasonable shear strainfield, so it can be used for both thick and thin plate analysis. Based on updated Lagrange (U.L.)scheme, Newmark integration method is used for the time stepping of structural dynamic responses.2、In order to express aerodynamic forces in time domain, the aerodynamic influencingcoefficients matrices which were obtained by doublet lattice method are approximated as rationalfunctions via Roger method. Then the expressions of time domain aerodynamic forces were derivedand programmed. The aerodynamic module was incorporated into the solver of structural response ina tight coupling manner, and then calculation of nonlinear aeroelastic response can be implemented.3、The nonlinear aeroelastic responses of a high aspect ratio wing was calculated by the methodpresented in this paper, the obtained critical flutter speeds have been compared to the results generatedby Nastrasn. It is showed that the method developed in this paper is able to produce reasonable andaccurate results, and can be used for nonlinear aeroelastic response calculation of high aspect ratiowing for practical engineering. Finally, the response characteristics of the nonlinear system areanalysed, where the properties of limit cycle oscillation are discussed.